Fix testing suite

The testing was borked and needed to be overhauled.

- Updated to chefspec 4
- Updated to FoodCritic 4
- Moved testing to Rakefile
- Added Ruby 2.1.5 to Travis testing
- Added Ubuntu 14.04 to test kitchen
- Fixed RuboCop config

All tests pass (RSpec, RuboCop, FoodCritic, Kitchen)