Updates to support most recent Ember Data conventions

More recent Ember Data requires all JSON keys to use camel casing instead of underscores. In addition, the outer key with name of relation needs to be pluralized when it contains a list of model instances. See documentation for [DS.RESTAdapter](http://emberjs.com/api/data/classes/DS.RESTAdapter.html).

This makes use of the Python inflection library which can convert between both camel case and underscore formatting, as well as singular and plural tenses of english words.