Add persona + gate-keeper routing (bug 982873)

What this branch does:

* Add faked persona integration (via stubbyid.js) + ui tests to cover redirection to a pin view. 
* Add fake verification
* Add fake logout.
* Add a user model to track the `app.user.get('logged_in')` state and fire events accordingly.
* Add a gatekeeper to the routing (using the brand-new Backbone.router.execute override.
* Refactor unit tests to use the same server as the uitests.
* Refactor the overall app architecture to remove duplication and smooth out some kinks.