Fix wrong exit status for tests

  Runing `gulp test` reported the wrong exit code for failing tests (always 0).
  As a workaround, call Makefile's `test` target instead.

Update Travis settings

  Start a mongoDB instance on boot

Update JSHint prefs

  Use node best practices' [recommendations][1]

[1]: https://github.com/felixge/node-style-guide#nodejs-style-guide
WIP Refactor backend into RESTful API

  Move ATM api into a separate Router.

Update tests and dependencies

  Add #beforeEach and #after hooks for DB setup and teardown.