A pile of changes to get the asset path in trusty-cms working.

Application file has been updated to enable the asset pipeline, and css, javascript and image files have been moved to
app assets. I've left them in public for now, though, while I determine the final way we should have this set up. Once
we do, the generator files in Radiant will need to be updated to produce this new setup.

Additionally, the application.rb file has had a hack added to it to keep Rack::Cache from returning empty 304 responses
for assets. This doesn't feel like the long term solution, but it's working for now.