diff --git a/package.json b/package.json
index 6990d78..c65c910 100644
--- a/package.json
+++ b/package.json
@@ -19,7 +19,7 @@
   },
   "devDependencies": {
     "codecov": "3.0.2",
-    "expect": "1.20.2",
+    "expect": "23.6.0",
     "mocha": "3.4.2",
     "nodemon": "1.11.0",
     "npm-run-all": "4.1.3",
diff --git a/yarn.lock b/yarn.lock
index cb950ca..d0e6248 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2,6 +2,20 @@
 # yarn lockfile v1
 
 
+"@babel/code-frame@^7.0.0-beta.35":
+  version "7.0.0"
+  resolved "https://registry.yarnpkg.com/@babel/code-frame/-/code-frame-7.0.0.tgz#06e2ab19bdb535385559aabb5ba59729482800f8"
+  dependencies:
+    "@babel/highlight" "^7.0.0"
+
+"@babel/highlight@^7.0.0":
+  version "7.0.0"
+  resolved "https://registry.yarnpkg.com/@babel/highlight/-/highlight-7.0.0.tgz#f710c38c8d458e6dd9a201afb637fcb781ce99e4"
+  dependencies:
+    chalk "^2.0.0"
+    esutils "^2.0.2"
+    js-tokens "^4.0.0"
+
 abbrev@1:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/abbrev/-/abbrev-1.1.0.tgz#d0554c2256636e2f56e7c2e5ad183f859428d81f"
@@ -28,6 +42,10 @@ ansi-regex@^2.0.0:
   version "2.1.1"
   resolved "https://registry.yarnpkg.com/ansi-regex/-/ansi-regex-2.1.1.tgz#c3b33ab5ee360d86e0e628f0468ae7ef27d654df"
 
+ansi-regex@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.yarnpkg.com/ansi-regex/-/ansi-regex-3.0.0.tgz#ed0317c322064f79466c02966bddb605ab37d998"
+
 ansi-styles@^2.2.1:
   version "2.2.1"
   resolved "https://registry.yarnpkg.com/ansi-styles/-/ansi-styles-2.2.1.tgz#b432dd3358b634cf75e1e4664368240533c1ddbe"
@@ -215,7 +233,7 @@ chalk@^1.0.0:
     strip-ansi "^3.0.0"
     supports-color "^2.0.0"
 
-chalk@^2.1.0:
+chalk@^2.0.0, chalk@^2.0.1, chalk@^2.1.0:
   version "2.4.1"
   resolved "https://registry.yarnpkg.com/chalk/-/chalk-2.4.1.tgz#18c49ab16a037b6eb0152cc83e3471338215b66e"
   dependencies:
@@ -373,7 +391,7 @@ deep-extend@~0.4.0:
   version "0.4.2"
   resolved "https://registry.yarnpkg.com/deep-extend/-/deep-extend-0.4.2.tgz#48b699c27e334bf89f10892be432f6e4c7d34a7f"
 
-define-properties@^1.1.2, define-properties@~1.1.2:
+define-properties@^1.1.2:
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/define-properties/-/define-properties-1.1.2.tgz#83a73f2fea569898fb737193c8f873caf6d45c94"
   dependencies:
@@ -400,6 +418,10 @@ diff@3.2.0:
   version "3.2.0"
   resolved "https://registry.yarnpkg.com/diff/-/diff-3.2.0.tgz#c9ce393a4b7cbd0b058a725c93df299027868ff9"
 
+diff@^3.2.0:
+  version "3.5.0"
+  resolved "https://registry.yarnpkg.com/diff/-/diff-3.5.0.tgz#800c0dd1e0a8bfbc95835c202ad220fe317e5a12"
+
 duplexer@~0.1.1:
   version "0.1.1"
   resolved "https://registry.yarnpkg.com/duplexer/-/duplexer-0.1.1.tgz#ace6ff808c1ce66b57d1ebf97977acb02334cfc1"
@@ -489,15 +511,6 @@ es-abstract@^1.4.3:
     is-callable "^1.1.3"
     is-regex "^1.0.4"
 
-es-abstract@^1.6.1:
-  version "1.7.0"
-  resolved "https://registry.yarnpkg.com/es-abstract/-/es-abstract-1.7.0.tgz#dfade774e01bfcd97f96180298c449c8623fb94c"
-  dependencies:
-    es-to-primitive "^1.1.1"
-    function-bind "^1.1.0"
-    is-callable "^1.1.3"
-    is-regex "^1.0.3"
-
 es-to-primitive@^1.1.1:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/es-to-primitive/-/es-to-primitive-1.1.1.tgz#45355248a88979034b6792e19bb81f2b7975dd0d"
@@ -518,6 +531,10 @@ escape-string-regexp@1.0.5, escape-string-regexp@^1.0.2, escape-string-regexp@^1
   version "1.0.5"
   resolved "https://registry.yarnpkg.com/escape-string-regexp/-/escape-string-regexp-1.0.5.tgz#1b61c0562190a8dff6ae3bb2cf0200ca130b86d4"
 
+esutils@^2.0.2:
+  version "2.0.2"
+  resolved "https://registry.yarnpkg.com/esutils/-/esutils-2.0.2.tgz#0abf4f1caa5bcb1f7a9d8acc6dea4faaa04bac9b"
+
 etag@~1.8.0:
   version "1.8.0"
   resolved "https://registry.yarnpkg.com/etag/-/etag-1.8.0.tgz#6f631aef336d6c46362b51764044ce216be3c051"
@@ -546,17 +563,16 @@ expand-range@^1.8.1:
   dependencies:
     fill-range "^2.1.0"
 
-expect@1.20.2:
-  version "1.20.2"
-  resolved "https://registry.yarnpkg.com/expect/-/expect-1.20.2.tgz#d458fe4c56004036bae3232416a3f6361f04f965"
+expect@23.6.0:
+  version "23.6.0"
+  resolved "https://registry.yarnpkg.com/expect/-/expect-23.6.0.tgz#1e0c8d3ba9a581c87bd71fb9bc8862d443425f98"
   dependencies:
-    define-properties "~1.1.2"
-    has "^1.0.1"
-    is-equal "^1.5.1"
-    is-regex "^1.0.3"
-    object-inspect "^1.1.0"
-    object-keys "^1.0.9"
-    tmatch "^2.0.1"
+    ansi-styles "^3.2.0"
+    jest-diff "^23.6.0"
+    jest-get-type "^22.1.0"
+    jest-matcher-utils "^23.6.0"
+    jest-message-util "^23.4.0"
+    jest-regex-util "^23.3.0"
 
 express@4.15.3:
   version "4.15.3"
@@ -697,7 +713,7 @@ fstream@^1.0.0, fstream@^1.0.10, fstream@^1.0.2:
     mkdirp ">=0.5 0"
     rimraf "2"
 
-function-bind@^1.0.2, function-bind@^1.1.0:
+function-bind@^1.0.2:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/function-bind/-/function-bind-1.1.0.tgz#16176714c801798e4e8f2cf7f7529467bb4a5771"
 
@@ -904,22 +920,12 @@ is-arrayish@^0.2.1:
   version "0.2.1"
   resolved "https://registry.yarnpkg.com/is-arrayish/-/is-arrayish-0.2.1.tgz#77c99840527aa8ecb1a8ba697b80645a7a926a9d"
 
-is-arrow-function@^2.0.3:
-  version "2.0.3"
-  resolved "https://registry.yarnpkg.com/is-arrow-function/-/is-arrow-function-2.0.3.tgz#29be2c2d8d9450852b8bbafb635ba7b8d8e87ec2"
-  dependencies:
-    is-callable "^1.0.4"
-
 is-binary-path@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/is-binary-path/-/is-binary-path-1.0.1.tgz#75f16642b480f187a711c814161fd3a4a7655898"
   dependencies:
     binary-extensions "^1.0.0"
 
-is-boolean-object@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/is-boolean-object/-/is-boolean-object-1.0.0.tgz#98f8b28030684219a95f375cfbd88ce3405dff93"
-
 is-buffer@^1.1.5:
   version "1.1.5"
   resolved "https://registry.yarnpkg.com/is-buffer/-/is-buffer-1.1.5.tgz#1f3b26ef613b214b88cbca23cc6c01d87961eecc"
@@ -930,7 +936,7 @@ is-builtin-module@^1.0.0:
   dependencies:
     builtin-modules "^1.0.0"
 
-is-callable@^1.0.4, is-callable@^1.1.1, is-callable@^1.1.3:
+is-callable@^1.1.1, is-callable@^1.1.3:
   version "1.1.3"
   resolved "https://registry.yarnpkg.com/is-callable/-/is-callable-1.1.3.tgz#86eb75392805ddc33af71c92a0eedf74ee7604b2"
 
@@ -948,22 +954,6 @@ is-equal-shallow@^0.1.3:
   dependencies:
     is-primitive "^2.0.0"
 
-is-equal@^1.5.1:
-  version "1.5.5"
-  resolved "https://registry.yarnpkg.com/is-equal/-/is-equal-1.5.5.tgz#5e85f1957e052883247feb386965a3bba15fbb3d"
-  dependencies:
-    has "^1.0.1"
-    is-arrow-function "^2.0.3"
-    is-boolean-object "^1.0.0"
-    is-callable "^1.1.3"
-    is-date-object "^1.0.1"
-    is-generator-function "^1.0.6"
-    is-number-object "^1.0.3"
-    is-regex "^1.0.3"
-    is-string "^1.0.4"
-    is-symbol "^1.0.1"
-    object.entries "^1.0.4"
-
 is-extendable@^0.1.1:
   version "0.1.1"
   resolved "https://registry.yarnpkg.com/is-extendable/-/is-extendable-0.1.1.tgz#62b110e289a471418e3ec36a617d472e301dfc89"
@@ -984,10 +974,6 @@ is-fullwidth-code-point@^1.0.0:
   dependencies:
     number-is-nan "^1.0.0"
 
-is-generator-function@^1.0.6:
-  version "1.0.6"
-  resolved "https://registry.yarnpkg.com/is-generator-function/-/is-generator-function-1.0.6.tgz#9e71653cd15fff341c79c4151460a131d31e9fc4"
-
 is-glob@^2.0.0, is-glob@^2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/is-glob/-/is-glob-2.0.1.tgz#d096f926a3ded5600f3fdfd91198cb0888c2d863"
@@ -998,10 +984,6 @@ is-npm@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/is-npm/-/is-npm-1.0.0.tgz#f2fb63a65e4905b406c86072765a1a4dc793b9f4"
 
-is-number-object@^1.0.3:
-  version "1.0.3"
-  resolved "https://registry.yarnpkg.com/is-number-object/-/is-number-object-1.0.3.tgz#f265ab89a9f445034ef6aff15a8f00b00f551799"
-
 is-number@^2.0.2, is-number@^2.1.0:
   version "2.1.0"
   resolved "https://registry.yarnpkg.com/is-number/-/is-number-2.1.0.tgz#01fcbbb393463a548f2f466cce16dece49db908f"
@@ -1020,7 +1002,7 @@ is-redirect@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/is-redirect/-/is-redirect-1.0.0.tgz#1d03dded53bd8db0f30c26e4f95d36fc7c87dc24"
 
-is-regex@^1.0.3, is-regex@^1.0.4:
+is-regex@^1.0.4:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/is-regex/-/is-regex-1.0.4.tgz#5517489b547091b0930e095654ced25ee97e9491"
   dependencies:
@@ -1030,10 +1012,6 @@ is-stream@^1.0.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/is-stream/-/is-stream-1.1.0.tgz#12d4a3dd4e68e0b79ceb8dbc84173ae80d91ca44"
 
-is-string@^1.0.4:
-  version "1.0.4"
-  resolved "https://registry.yarnpkg.com/is-string/-/is-string-1.0.4.tgz#cc3a9b69857d621e963725a24caeec873b826e64"
-
 is-symbol@^1.0.1:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/is-symbol/-/is-symbol-1.0.1.tgz#3cc59f00025194b6ab2e38dbae6689256b660572"
@@ -1064,12 +1042,51 @@ isstream@~0.1.2:
   version "0.1.2"
   resolved "https://registry.yarnpkg.com/isstream/-/isstream-0.1.2.tgz#47e63f7af55afa6f92e1500e690eb8b8529c099a"
 
+jest-diff@^23.6.0:
+  version "23.6.0"
+  resolved "https://registry.yarnpkg.com/jest-diff/-/jest-diff-23.6.0.tgz#1500f3f16e850bb3d71233408089be099f610c7d"
+  dependencies:
+    chalk "^2.0.1"
+    diff "^3.2.0"
+    jest-get-type "^22.1.0"
+    pretty-format "^23.6.0"
+
+jest-get-type@^22.1.0:
+  version "22.4.3"
+  resolved "https://registry.yarnpkg.com/jest-get-type/-/jest-get-type-22.4.3.tgz#e3a8504d8479342dd4420236b322869f18900ce4"
+
+jest-matcher-utils@^23.6.0:
+  version "23.6.0"
+  resolved "https://registry.yarnpkg.com/jest-matcher-utils/-/jest-matcher-utils-23.6.0.tgz#726bcea0c5294261a7417afb6da3186b4b8cac80"
+  dependencies:
+    chalk "^2.0.1"
+    jest-get-type "^22.1.0"
+    pretty-format "^23.6.0"
+
+jest-message-util@^23.4.0:
+  version "23.4.0"
+  resolved "https://registry.yarnpkg.com/jest-message-util/-/jest-message-util-23.4.0.tgz#17610c50942349508d01a3d1e0bda2c079086a9f"
+  dependencies:
+    "@babel/code-frame" "^7.0.0-beta.35"
+    chalk "^2.0.1"
+    micromatch "^2.3.11"
+    slash "^1.0.0"
+    stack-utils "^1.0.1"
+
+jest-regex-util@^23.3.0:
+  version "23.3.0"
+  resolved "https://registry.yarnpkg.com/jest-regex-util/-/jest-regex-util-23.3.0.tgz#5f86729547c2785c4002ceaa8f849fe8ca471bc5"
+
 jodid25519@^1.0.0:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/jodid25519/-/jodid25519-1.0.2.tgz#06d4912255093419477d425633606e0e90782967"
   dependencies:
     jsbn "~0.1.0"
 
+js-tokens@^4.0.0:
+  version "4.0.0"
+  resolved "https://registry.yarnpkg.com/js-tokens/-/js-tokens-4.0.0.tgz#19203fb59991df98e3a287050d4647cdeaf32499"
+
 jsbn@~0.1.0:
   version "0.1.1"
   resolved "https://registry.yarnpkg.com/jsbn/-/jsbn-0.1.1.tgz#a5e654c2e5a2deb5f201d96cefbca80c0ef2f513"
@@ -1232,7 +1249,7 @@ methods@~1.1.2:
   version "1.1.2"
   resolved "https://registry.yarnpkg.com/methods/-/methods-1.1.2.tgz#5529a4d67654134edcc5266656835b0f851afcee"
 
-micromatch@^2.1.5:
+micromatch@^2.1.5, micromatch@^2.3.11:
   version "2.3.11"
   resolved "https://registry.yarnpkg.com/micromatch/-/micromatch-2.3.11.tgz#86677c97d1720b363431d04d0d15293bd38c1565"
   dependencies:
@@ -1430,23 +1447,10 @@ object-component@0.0.3:
   version "0.0.3"
   resolved "https://registry.yarnpkg.com/object-component/-/object-component-0.0.3.tgz#f0c69aa50efc95b866c186f400a33769cb2f1291"
 
-object-inspect@^1.1.0:
-  version "1.2.2"
-  resolved "https://registry.yarnpkg.com/object-inspect/-/object-inspect-1.2.2.tgz#c82115e4fcc888aea14d64c22e4f17f6a70d5e5a"
-
-object-keys@^1.0.8, object-keys@^1.0.9:
+object-keys@^1.0.8:
   version "1.0.11"
   resolved "https://registry.yarnpkg.com/object-keys/-/object-keys-1.0.11.tgz#c54601778ad560f1142ce0e01bcca8b56d13426d"
 
-object.entries@^1.0.4:
-  version "1.0.4"
-  resolved "https://registry.yarnpkg.com/object.entries/-/object.entries-1.0.4.tgz#1bf9a4dd2288f5b33f3a993d257661f05d161a5f"
-  dependencies:
-    define-properties "^1.1.2"
-    es-abstract "^1.6.1"
-    function-bind "^1.1.0"
-    has "^1.0.1"
-
 object.omit@^2.0.0:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/object.omit/-/object.omit-2.0.1.tgz#1a9c744829f39dbb858c76ca3579ae2a54ebd1fa"
@@ -1586,6 +1590,13 @@ prettier@1.12.1:
   version "1.12.1"
   resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.12.1.tgz#c1ad20e803e7749faf905a409d2367e06bbe7325"
 
+pretty-format@^23.6.0:
+  version "23.6.0"
+  resolved "https://registry.yarnpkg.com/pretty-format/-/pretty-format-23.6.0.tgz#5eaac8eeb6b33b987b7fe6097ea6a8a146ab5760"
+  dependencies:
+    ansi-regex "^3.0.0"
+    ansi-styles "^3.2.0"
+
 process-nextick-args@~1.0.6:
   version "1.0.7"
   resolved "https://registry.yarnpkg.com/process-nextick-args/-/process-nextick-args-1.0.7.tgz#150e20b756590ad3f91093f25a4f2ad8bff30ba3"
@@ -1811,6 +1822,10 @@ signal-exit@^3.0.0:
   version "3.0.2"
   resolved "https://registry.yarnpkg.com/signal-exit/-/signal-exit-3.0.2.tgz#b5fdc08f1287ea1178628e415e25132b73646c6d"
 
+slash@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/slash/-/slash-1.0.0.tgz#c41f2f6c39fc16d1cd17ad4b5d896114ae470d55"
+
 slide@^1.1.5:
   version "1.1.6"
   resolved "https://registry.yarnpkg.com/slide/-/slide-1.1.6.tgz#56eb027d65b4d2dce6cb2e2d32c4d4afc9e1d707"
@@ -1900,6 +1915,10 @@ sshpk@^1.7.0:
     jsbn "~0.1.0"
     tweetnacl "~0.14.0"
 
+stack-utils@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.yarnpkg.com/stack-utils/-/stack-utils-1.0.1.tgz#d4f33ab54e8e38778b0ca5cfd3b3afb12db68620"
+
 "statuses@>= 1.3.1 < 2", statuses@~1.3.1:
   version "1.3.1"
   resolved "https://registry.yarnpkg.com/statuses/-/statuses-1.3.1.tgz#faf51b9eb74aaef3b3acf4ad5f61abf24cb7b93e"
@@ -2005,10 +2024,6 @@ timed-out@^2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/timed-out/-/timed-out-2.0.0.tgz#f38b0ae81d3747d628001f41dafc652ace671c0a"
 
-tmatch@^2.0.1:
-  version "2.0.1"
-  resolved "https://registry.yarnpkg.com/tmatch/-/tmatch-2.0.1.tgz#0c56246f33f30da1b8d3d72895abaf16660f38cf"
-
 to-array@0.1.4:
   version "0.1.4"
   resolved "https://registry.yarnpkg.com/to-array/-/to-array-0.1.4.tgz#17e6c11f73dd4f3d74cda7a4ff3238e9ad9bf890"