Update TypeScript Fetch TypeScript version to 2.0.7

[leonyu]

PR checklist

• Read the contribution guildelines.
• Ran the shell/batch script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates)
• Filed the PR against the correct branch: master for non-breaking changes and 2.3.0 branch for breaking (non-backward compatible) changes.

Description of the PR

(details of the change, additional tests that have been done, reference to the issue for tracking, etc)

• Update TypeScript Fetch TypeScript version to 2.0.7
• Fix support for underscore casing in POST body

[leonyu]

The code was written against 2.2.0, and rebased.

I didn't run ./bin/{LANG}-petstore.sh, cause I couldn't get Maven to pass on master on my machine (OSX).

[wing328]

@leonyu I updated the TS Fetch Petstore sample in https://github.com/swagger-api/swagger-codegen/tree/leonyu-update_to_typescript_2 and got the following error when running the test locally:

default|leonyu-update_to_typescript_2⚡ ⇒ npm install

> fsevents@1.0.15 install /Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/tests/default/node_modules/fsevents
> node-pre-gyp install --fallback-to-build

[fsevents] Success: "/Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/tests/default/node_modules/fsevents/lib/binding/Release/node-v48-darwin-x64/fse.node" is installed via remote

> typescript-fetch-test@1.0.0 prepublish /Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/tests/default
> ./scripts/prepublish.sh


> typescript-fetch-api@0.0.0 prepublish /Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/builds/default
> tsc

typescript-fetch-test@1.0.0 /Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/tests/default
└─┬ typescript-fetch-api@0.0.0 
  ├── @types/core-js@0.9.34 
  ├── @types/isomorphic-fetch@0.0.31 
  ├── @types/node@6.0.46 
  ├── core-js@2.4.1 
  └─┬ isomorphic-fetch@2.2.1 
    ├─┬ node-fetch@1.6.3 
    │ └─┬ encoding@0.1.12 
    │   └── iconv-lite@0.4.13 
    └── whatwg-fetch@1.0.0 

typings WARN deprecated 6/2/2016: "registry:dt/chai#3.4.0+20160317120654" is deprecated (updated, replaced or removed)
typings WARN deprecated 6/14/2016: "registry:dt/es6-promise#0.0.0+20160423074304" is deprecated (updated, replaced or removed)
typings WARN deprecated 10/28/2016: "registry:dt/mocha#2.2.5+20160317120654" is deprecated (updated, replaced or removed)

├── chai (global)
├── es6-promise (global)
└── mocha (global)

node_modules/typescript-fetch-api/dist/api.d.ts(1,1): error TS1084: Invalid 'reference' directive syntax.
ts-loader: Using typescript@1.8.10 and /Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/tests/default/tsconfig.json
Hash: 18e866baa0cf3e197705
Version: webpack 1.13.3
Time: 2487ms
                          Asset    Size  Chunks             Chunk Names
  ./dist/test.webpack-bundle.js  225 kB       0  [emitted]  app
./dist/vendor.webpack-bundle.js  124 kB       1  [emitted]  vendor
   [0] multi vendor 28 bytes {1} [built]
    + 91 hidden modules

ERROR in /Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/tests/default/node_modules/typescript-fetch-api/dist/api.d.ts
(1,1): error TS1084: Invalid 'reference' directive syntax.
TypeScript error: /Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/tests/default/node_modules/typescript-fetch-api/dist/api.d.ts(1,1): Error TS1084: Invalid 'reference' directive syntax.

npm ERR! Darwin 15.6.0
npm ERR! argv "/usr/local/Cellar/node/6.5.0/bin/node" "/Users/williamcheng/.node/bin/npm" "install"
npm ERR! node v6.5.0
npm ERR! npm  v3.10.6
npm ERR! code ELIFECYCLE
npm ERR! typescript-fetch-test@1.0.0 prepublish: `./scripts/prepublish.sh`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the typescript-fetch-test@1.0.0 prepublish script './scripts/prepublish.sh'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the typescript-fetch-test package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     ./scripts/prepublish.sh
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs typescript-fetch-test
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls typescript-fetch-test
npm ERR! There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     /Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/tests/default/npm-debug.log
default|leonyu-update_to_typescript_2⚡ ⇒ pwd
/Users/williamcheng/Code/swagger-api/swagger-codegen/samples/client/petstore/typescript-fetch/tests/default

[leonyu]

Sorry, I am swamped with other work. Will take a look later this week.

[wing328]

Please take your time. Let us know if you need any help.

[wing328]

Closed via #6130