Initial Backbone setup.

I used the `rails-backbone` gem to bootstrap a Backbone app. Right now, anonymous users should see a static index page and authenticated users should cause the Backbone app to be initialized with a greeting.

![greeting](https://f.cloud.github.com/assets/46992/2021520/41c23d52-8840-11e3-80c7-d74a8c103ff4.png)