Remove traceback upon exit in plain command line program

[britth]

For our base program if we don't get around to finishing working with curses or another library, we can remove the traceback message upon exit (CTRL-C) with an execption, like here: http://stackoverflow.com/questions/7073268/remove-traceback-in-python-on-ctrl-c

This could be a simple way to make the base version of the program look better for the user.