Updated script to use the argparse python module, which prints a slightl...

Updated script to use the argparse python module, which prints a slightly nicer example and usage message, and puts some of the logic into the arparse object

This does change the default output when arg's are wrong from exiting 3
To exiting to a '2' state

I would have suggested merging it into a separate branch to check it out, but I wasn't sure how to request that in a Pull request.