Remove use of GamePad and GamePadShift

[FoamyGuy]

#4940 in the core will remove gamepad and gamepadshift.

This library makes use of these objects to handle the buttons for some of the devices that are supported. We'll need to change over this library to use the newer keypad functionality when these do get removed from the core.

[caternuson]

yep:
https://forums.adafruit.com/viewtopic.php?f=65&t=183536

[FoamyGuy]

#48 (marked as draft currently) implements this change.

[FoamyGuy]

closed by #48