add the license file
modify README
copy prototype files from raspberry-pi-python-sample [1][2]

[1] https://github.com/leathersole/raspberry-pi-python-sample/blob/master/sound-test/soundkey.py
[2] https://github.com/leathersole/raspberry-pi-python-sample/blob/master/sound-test/soundkey-nogpio-pygame.py