Keypad Test, by hap, 15-02-06

press a chip8 key and the pressed char will light up
if you want to do something funny, soft-reset the chip8/emulator over and over,
and the sprite layout will become messed up ;p

chip8 keypad:
1 2 3 c
4 5 6 d
7 8 9 e
a 0 b f

