Introduce role-based serverspec testing, powered by everybody's favorite hobo

This allows for writing and running acceptance tests for specific roles
(dist/role/manifests/*.pp) and spinning up a Vagrant AWS machine with that
role, then running the appropriate serverspec tests against it.
Add a placeholder spec dir for artichoke aka puppetmaster
Merge pull request #25 from rtyler/vagrant-serverspec-and-roles

Introduce role-based serverspec testing, powered by Vagrant