Killpack/auth *WIP* *WIP* *WIP*

WIP.

It's gonna work like this:
- You type in your username and password, which hits the `authorizations` endpoint. On successful authentication, it returns your auth token.
- Ember stores this auth token somewhere and uses it to make requests from thereon out.
It means that this controller has a dependency on the `sessions` controller. Without this, the `property` and `get` calls below wouldn't work, since they reference a property on the `sessions` controller.