no longer draw in secondary thread during app launch (closes #117)
eliminate "application is ready for action" mechanism (closes #119)
invoke PlayView's delayedUpdate instead of setNeedsLayout after zoom
refactoring PlayView and layer delegate system

change details
- PlayView now stores layer delegates in an array so that they can be
  iterated for notifications and updates
- PlayViewLayerDelegate now stores a reference to its main view
- PlayViewLayerDelegateBase now creates the CALayer and adds
  it to its main view (instead of PlayView)