Add before and after suite

Addresses issue https://github.com/modocache/Quick/issues/2. 

Adds optional closures that can be run before and after the suite.

Comments are inline. I'd love to get feedback!
> It looks like ginkgo only let's you define one per suite

Hmm, I wonder whether that's by choice. Wish I had time to look into it and maybe even file an issue...