Short reactive gesture reactor

[fabb]

⚠️ Not yet finished, do not merge

Introduced IntegratedReactiveGestureReactor which does not use the semi-imperative way of receiving gesture events.

The unit tests still need to be developed, some way needs to be found to create mock gesture events.

[fabb]

For mocking, it would be better if IntegratedReactiveGestureReactor was initialized with events of type ControlEvent<UIGestureRecognizerType>. Unfortunately RxCocoa's rx_event creates ControlEvent<UIGestureRecognizer> which seems not castable. Asked a question about this on StackOverflow: http://stackoverflow.com/questions/35862869/swift-covariant-generics

✅ ok, found a solution: d3c73b3

[fabb]

this unit test fails - no idea why