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).
This describes `viewDidLoad`, but the setup (i.e.: calling `viewDidLoad`) is done in the describe block one level above this one. I think I'd structure this differently:

```swift
describe("after the view has been loaded") {
  beforeEach { viewController.view /* trigger a view load */ }
  it("loads the table view with one cell") { /* ... */ }

  describe("didSelectRowAtIndexPath") {
    it("deletes the selected row and reloads the tableView's data") { /* ... */ }
  }
}
```

Definitely a matter of taste, though--if you disagree you can feel free keeping it this way. Certainly not a merge blocker. :monkey: