Adding Demo Code

This adds a few commands to the user prompt:
  1) "demo" - takes two trains that it will track.
  2) "c" - perform one iteration of find random destinations
     and send trains there.
  3) "loop" - continually send trains to random destinations.

Unsure whether "loop" works perfectly, since its hard to
tell if "loop" is the issue or if routing is the issue
when they screw up.