Make Cozmo Play a Series of Notes

[gbroques]

Cozmo needs to be able to play a series of notes.

We'll add sometimes playing a wrong note in issue #11.

This will involve adding a play_notes() method in the SongRobot class.

Something like:

def play_notes(notes: List[Note]) -> None:
    for note in notes:
        await self.play_note(note)