Fixed interaction with gesture recognizers
Fixed interaction with gesture recognizers

If the range slider is placed on a view with a gesture recognizer (eg a scroll view)
the gesture recognizer can grab touch events making the slider difficult to control.
The Apple documentation for the UIView gestureRecognizerShouldBegin method mentions
that this method is used by UISlider to overcome this issue, so this is the approach
this patch uses.

The new page sheet presentation style in iOS 13 makes it more likely that the view
the range slider is on will have a gesture recognizer, and therefore be effected by
this problem.

While debugging this issue similar symptoms to issue #69 ("Handle stays enlarged
when tapped during drag of parent view") were encountered and fixed. The exact
reproduction steps described in issue 69 haven't been retested, but it's possible
this patch also fixes that issue.

TomThorpe/TTRangeSlider