Cachebusters needed

[bemurphy]

I'm not sure the best way to approach this, but as-is this prevents rails_asset_ids from getting generated. Since the assets no longer exist in the expected location, the rails tag helpers can't find a file for mtime stats.

I believe the heroku deploy process would result in mtime on assets being the time of deploy, so setting an initializer to set ENV["RAILS_ASSET_ID"] to be the start time would probably be good enough. Perhaps just a line in the readme?