Refactored setProgress: animated:

Removed calls to ‘self.progress = progress’
Removed popUpViewDidHide from protocol

Use a completion block instead. Also set popUpView transform to
CATransform3DIdentity after hiding. This ensures that the popUpView
always appears at the correct size when displaying without animation.
Adjusted animation timings

When the view was hidden automatically a slower animation was less
abrupt. Now that showing and hiding the popUpView is done manually, it
makes sense to speed up the animations, giving them a bit more spring.