Add a JavaScript test suite

Implements a additional controller which is not included per default, but when invoked with a rake task. Uses mocha, chai and sinon for JavaScript specs. This refs #123.

Run `rake test_js` to serve test suite at /test.

I also added a first test for the Story model. There you can see that the JS specs are very similar to the ruby specs. 

Please fell free to add more tests as I'm a little out of time right now.