Removed unnecessary -setDelegate:self from gestureRecognizer.

On iOS 5.0, if you -initWithTarget:action: and also -setDelegate: on
UIGestureRecognizer, you'll actually break the invocation, and the
cell won't be notified on a pan gesture.  This commit removes the
unnecessary -setDelegate: call and enables use on iOS 5.0.

For (slightly) more details, see http://stackoverflow.com/q/8535958