First attempted pull request

Hi Sophia -- I think I have merged the changes you made with those I made. For some reason I can't get Montage to compile on my laptop so I can't test the whole thing here. But I can run the setup.py script and it finishes (feeling pretty proud of myself..).

I'll do some quick tests tomorrow to make sure this merged version actually runs, so you can delay actually accepting the PR until after you hear from me.