Upgrade to python3

[aprajita]

This shouldn't be too difficult! Just some print functions I think... I'll let you know when it is ready for code review, @drphilmarshall

[drphilmarshall]

Thanks, @aprajita ! I just merged a similar PR from a different user, so much of what you want to do may already be in place. See if you can run the code in python 3 after doing a git pull from drphilmarshall:master? There may still be small tweaks needed.