Fix Travis CI build

.travis.yml

@@ -1,22 +1,27 @@
 sudo: required
 dist: trusty
+env: DISPLAY=':99.0'
 language: node_js
 
-cache:
-  directories:
-    - node_modules
-    - ~/.selenium-assistant
+addons:
+  apt:
+    update: true
+    sources:
+      - google-chrome
+    packages:
+      - dpkg
+      - google-chrome-stable
 
 node_js:
-  - '6'
+  - '12'
   - '8'
+  - '6'
 
 install:
   - npm install
 
 # Read more here: https://docs.travis-ci.com/user/gui-and-headless-browsers/#Using-xvfb-to-Run-Tests-That-Require-a-GUI
 before_script:
-  - "export DISPLAY=:99.0"
   - "sh -e /etc/init.d/xvfb start || echo \"Unable to start virtual display.\""
   - sleep 3 # give xvfb some time to start
 

README.md

@@ -71,9 +71,6 @@ and error with have an 'id' and 'message' parameter.
     This method expected a testSuiteId, a browser name and the release version
     and it will return a subscription.
 
-    The gcmSenderId and vapidPublicKey parameters are options BUT Chrome
-    requires one of them to work, otherwise you must catch the error.
-
     http://localhost:8090/api/get-subscription/
 
     **Input**
@@ -82,7 +79,6 @@ and error with have an 'id' and 'message' parameter.
         testSuiteId: <Test Suite ID Number>,
         browserName: <'chrome' | 'firefox'>,
         browserVersion: <'stable' | 'beta' | 'unstable' >,
-        gcmSenderId: <Your GCM Sender ID>,
         vapidPublicKey: <Base64 URL Encode Vapid Public Key>
     }
     ```