BF: add 'height' to list of selectable units in prefs and exp settings
DOC: microphone minor clean-up

also: .playback() now has a block parameter, to override default block
RF: microphone.py replace time.time() with core.getTime()

also time.sleep() -> core.wait()
DOC: install avbin on mac; microphone command-line test
Merge pull request #270 from jeremygray/master

minor DOC and RF