publish to pypi and tag releases

[dzheng256]

We should properly manage our package versioning and package up releases (e.g. 0.1.0, 0.2.0, etc) and publish them to pypi so people can pip install from there, instead of directly installing from our master branch, which may or may not be in a broken state. Each release to pypi should come with either bugfixes or new features, and we should definitely make sure whatever we are publishing actually works properly (adding more tests will help ensure this).

I think it would be reasonable to make a 0.1.0 release and publish that to pypi after we resolve #3 and (hopefully) remove the bloated nltk dependency