Updated dependencies

Currently, cartilage references backbone-rails (https://github.com/aflatter/backbone-rails) which is tied to backbone versions and not very active.  Since it includes underscorejs it is now fairly behind and missing some very nice to have elements.  Given this and other depenedency related issues we've run into, it would be nice to consider using a different set of gems altogether (https://github.com/aflatter/backbone-rails) or break them out so they are local to cartilage, e.g., 'cartilage-backbone-rails', 'cartilage-underscore-rails', etc.