Kivy crash course 14: Using a ScreenManager HD

This time, I cover the basic ideas behind using a ScreenManager widget to add different screens to your app and switch between them with a range of fancy transitions. Links: - Collected files: https://github.com/inclement/kivycrashcourse/tree/master/video14-using_a_screenmanager - Code at start: https://github.com/inclement/kivycrashcourse/blob/master/video14-using_a_screenmanager/before.py - Code at end: https://github.com/inclement/kivycrashcourse/blob/master/video14-using_a_screenmanager/after.py - Images used in code: https://github.com/inclement/kivycrashcourse/blob/master/video14-using_a_screenmanager/colours.png and https://github.com/inclement/kivycrashcourse/blob/master/video14-using_a_screenmanager/colours2.png