Add frontend caching with localStorage

[whastings]

I want to use the Rails stale? method to respond with 304s when the data for an Ajax request hasn't changed.

I'll need to make sure that a category's updated_at is updated when one of its resources or child categories is updated via touch.

After some investigation, I found that the user specific data (favorite IDs for resources) makes caching via HTTP overly complex. Instead, I want to work on implementing caching via the browser's localStorage.