Rubocop plugin

Created a plug-in to run Rubocop against a cookbook before uploading, based completely on the Foodcritic plug-in.

There's more I would like to do with it if I can figure out the rubocop API more, but this does the basic - runs rubocop, fails if 'epic_fail' is set to true.

I'm still learning git (along with Chef & Ruby), so forgive me if I've done the branching / pull-request wrong somehow.