Convert all remaining jQuery interactions to Backbone

Continuing where we left off, we further organize our code by moving the event handling for the Thumbnails container and the conditional hiding of the header banner into two new Backbone views. Now we have no explicit jQuery DOM traversal anywhere in our application, and all view updates are driven by the Featured Artwork model's data. Application initialization consists of defining the models and views, and Backbone takes it from there.
Merge pull request #6 from kadamwhite/backbone-final

Convert all remaining jQuery interactions to Backbone