Commence style policing!

RFC @sobering, @johnTurknett, @jamesbrink — This closes #17 by including our good friend Rubocop.  If you're not familiar Rubocop is a static analyzer that relies on the Ruby styleguide and our own configuration (found in `.rubocop.yml`).  

In addition to the configuration file you'll see `.rubocop_todos.yml`, these are our current styleguide violations that we're given a pass on (when you run `rubocop` it won't report these known ones) so we can keep moving forward.  Over time we can knock out these and in time remove the todo file entirely, that's the goal at least.  Just for the record a lot of the current violations are the result of generated Rails code, not necessarily things we've written thus far.

In addition to Rubocop I went ahead and fixed one of the first violations it was upset about:  Missing UTF-8 magic comments from all the Ruby files.