Display file stats for user.  Feature #9305

The UI looks like this:
![user_stats](https://cloud.githubusercontent.com/assets/298865/5322312/033ecea8-7c8a-11e4-895c-c228cecc6868.png)

The new "better" convention for these is with tap and let see: https://github.com/projecthydra/sufia/blob/master/spec/controllers/single_use_links_controller_spec.rb#L5-L11