Update ember

Update ember to canary release for query param support and ember-data to
beta.2. Vendors ember, ember-data and handlebars over using the
`*-source` gems via `ember-rails` since `ember-source` does not support
canary releases. Only require the `ember-rails` engine and not the
`*-source` gems.

Update to use new APIs
* Use `this.store` over the DS.Store subclasses
* Place all actions in an `actions` object in the controller.
* Remove use of transactions
* Use `then` to deal with promises instead of setting callbacks using
  `on` or `one`.

Update server-side code for compatibility with beta of ember-data:
* Update `DeliverySerializer` to `include` `receipts` as a top level key
  in the JSON response and embed their ids.
* Remove the custom `root` in `UserRolesController`
* Always include a unique `id` in a serialized `user` for compatibility
  with new ember-data API