Improvements: dismissOnTap and dimissOnPassthroughViewTap properties; optional dismissCompletionBlock

- Added options to dismiss on inner tap and dimiss on passthrough tap (`dismissOnTap` and `dimissOnPassthroughViewTap` BOOL properties).
- Added optional `^dismissCompletionBlock(WYPopoverController *dimissedController`) block property. Can be used in addition to, or in place of, the delegate's `popoverControllerDidDismissPopover:` method.
- Removed old unused touch code