Feature/load json fixtures

- Allows us to load in json fixtures using requirejs
- Uses `json` plugin from https://github.com/millermedeiros/requirejs-plugins to load in json
- This has a stupid syntax, but I think it's better than adding a huge object into our tests. 

Usage:
``` js
define([
  'json!fixtures/myFixture.json'
],
function (myFixture) {
...
});
```