Add code coverage reports

Add [Coveralls][1] support via istanbul :lipstick: .

 - Update `Makefile` targets and `gitignore` list.

 - Update config exports

  * Use an index to make imports less verbose:

      `require('../config')`

Misc

 - Bump dependencies
 - Refactor to use newer deps
 - Update deprecated API calls
 - Use newer Express style for json responses
 - Update bodyParser
 - Add application validation middleware
 - Return `201` on content creation

Tests

 - Refactor test folder layout (env, fixtures and acceptance)
 - Move test helper into `support` folder
 - Rename specs

[1]: coveralls.io