fix for when_pressed and uiactionsheet
fix for when_pressed and uiactionsheet

without checking for recognizer.state==UIGestureRecognizerStateBegan, if you call a new UIActionSheet from inside a when_pressed handler two identical `UIActionSheet`s are instantiated and displayed.
hboon/BubbleWrap,andersennl/BubbleWrap,earthrid/BubbleWrap,dam13n/BubbleWrap,fandor/BubbleWrap