Rip out cancan and rolify, shouldn't have had them to start.

I used [Rails Composer](http://railsapps.github.io/rails-composer/) to start this app and thought I would want cancan in there, but turns out it just annoys me sitting around not being used. I'll add it back later if we need it.

This PR is going to require a rake db:drop as I’m modifying model history by ripping out a migration :grin: