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.
Alrighty, I think it's because we want the user to be able to logout from anywhere in the app. Actions get fired on the current controller, and if nothing handles them, they bubble up through any parent controllers. Since we want the user to be able to logout regardless of the current controller, we have to put this action in the outermost controller, ie. the application controller. If we stick this action in the sessions controller, the user will only be able to log out if they're looking at the login screen.

Here's a link about action bubbling: http://emberjs.com/guides/templates/actions/#toc_action-bubbling