RF: remove microphone.switchOff()

but keep the function defn for now just for backwards compatibility
RF: better sound in emulator.py
Merge pull request #258 from jeremygray/master

 remove microphone.switchOff()
RF: simplified playback() for microphone
RF: allow sound.Sound().play()
ENH: enable Sound.play() forSoundPpygame too
Merge pull request #259 from jeremygray/master

more minor RF sound in microphone