Remove `berks test` and kitchen related things

Loading Test Kitchen actually costs us ~0.5 second when running the CLI. Unlike Octokit, we can't push the require statement down into the stack since we are stealing options from Kitchen's Thor.

I think this is the first step in extracting the generators into their own gem. I don't actually think this should be merged - it's more of a discussion point around how we can speed up CLI loadtimes.