Update to work with latest orbit/ember-orbit

* Import AMD builds to work as modules in ember-cli
* Introduce custom Schema to define `idField`
* Serialize PostRoute based on slug

TODO:
* Fix server response to `/posts/:slug` to return single post in object, not array (to conform with current JSON API spec)
Merge pull request #3 from dgeb/update-orbit

Update to work with latest orbit/ember-orbit