Add section about testing UIKit interaction with Quick.

Hello,

I've been using Quick for unit testing view controllers. I saw issue #39 requested a section about UIKit testing, so I thought I'd write something up. Let me know if you'd like any changes. There is a reference application implementing the Swift example tests (and code to make the tests pass) located here: [Reference Swift Application](https://github.com/sidraval/DolphinTableViewApp).
Typo: `__block`, not `_block`. :point_up: :bulb: