BF / ENH: Fixed OSX iohub process not closing.

BF: Now ioHub Process closes properly, either when
ioHubConnection.quit() is called, or when the object is GC.

BF: The failsafe check for killing an old ioHub process that is still
running when a new ioHub connection is created works on OSX. (Jeremy
Gray)

ENH: Added the new example I did yesterday. Will clean up the iohub demo
dir for psychopy once confirmation is given  about what demo's will be
included with release.