break/stop on MSG line
* Added HIT MSG event.
* Added code to break/stop upon encountering MSG line in GCODE
* Fix bug, Save-As didn't update document title.
Fix Unicode strings and added error checking.
* Make sure strings sent to pySerial are ascii, apparently it doesn't
  like Unicode strings.
* Added try/catch block when trying to open serial port.
* Minor message change when serial port is not successfully open.