Usage:

% metahost -v -b 57600 -p COM3 <file.gcode> 

If start.gcode and/or end.gcode are present, prepend/append these

TODO/ideas:
o Ctrl-c: If we're in the middle of the first heating phase, it will move down
  before aborting
o Implement some kind of diagnostics mode to test that the reprap
  responds correctly to commands (cmd-line exerciser?)
o Sometimes metahost reports unexpected response: (empty line)
o Sometimes, clean shutdown fails to turn off motor (premature exit?)
o Subtract heating time/raft from ETA timer?
o Update ETA every second (don't wait for a response)
o Is it possible to check if a serial port is in use and not autoconnect to that one?
o Print real time spend (statistics on exit)
o Missing temperature reporting: fflush?