Add documentation and docstrings

[AaronDJohnson]

Almost all of the functions need documentation and docstrings. Many of the functions are documented in part in the README.MD file. A good first step is to come up with conventions for docstrings that people can follow.

[davecwright3]

@AaronDJohnson I've already started work on this with mkdocs https://www.mkdocs.org/ and NumPy-style docstrings. The results will look similar to https://andrea-mitridate.github.io/PTArcade/, including auto-docs from the docstrings.

Do these choices sound reasonable? I can open a draft PR sometime tomorrow with my work.

[AaronDJohnson]

I think that looks great! Let's open a PR. Can you post an example of the docstring style? It would be useful for people to have something to go off of.

[davecwright3]

@AaronDJohnson see #62. I'm fine switching to Google or Sphinx style if people prefer that.