Summary:This fixes issues with other view (like the Navigator) stealing the responder and becoming interactive while the user is dragging the slider.
From [documentation](https://facebook.github.io/react-native/docs/gesture-responder-system.html):
- `onStartShouldSetResponder`: Does this view want to become responder on the start of a touch? -> Yes.
- `onResponderTerminationRequest`: Something else wants to become responder. Should this view release the responder? -> No.
Reviewed By: ericvicenti
Differential Revision: D3133337
fb-gh-sync-id: 3d7e1e6a2ed6fa605857cfb0549ffa71df85fd22
fbshipit-source-id: 3d7e1e6a2ed6fa605857cfb0549ffa71df85fd22