Fixed issue-29, unbalanced calls to begin/end appearance transitions

[OrkhanAlikhanov]

Fixed issue #29. Calling {begin,end}AppearanceTransition methods for modal transitions was causing the issue since UIKit was already calling them internally.

I did rigorous testing after fixing the issue with multiple setups (TabsContoller, NavigationDrawer, NavigationContoller, BottomNavigationBar) to try various transitions types, it never showed up again. I examined the view{Will,Did}{Appear,Disappear} call trace and it was exactly same for Motion and UIKit modal transitions. Example trace:

viewWillDisappear AppRootController
viewWillDisappear NavigationController
viewWillDisappear BottomNavigationController
viewWillAppear ModalViewController
viewDidAppear ModalViewController
viewDidDisappear AppRootController
viewDidDisappear NavigationController
viewDidDisappear BottomNavigationController
viewWillDisappear ModalViewController
viewWillAppear AppRootController
viewWillAppear NavigationController
viewWillAppear BottomNavigationController
viewDidAppear AppRootController
viewDidAppear NavigationController
viewDidAppear BottomNavigationController
viewDidDisappear ModalViewController

[daniel-jonathan]

Don't forget to send PRs to the development branch.