Add documentation

[wtbarnes]

Currently, the only documentation for this software lies in PDF format under docs. It would be preferable if the documentation were instead formatted in a markup language and rendered as a webpage (e.g. using tools like Sphinx or mkdocs). This would allow the documentation to be version controlled and thus more easily maintained. In this format, the documentation could also be hosted on a service such as Read the Docs that would allow it to be more discoverable.

Additionally, tools like Sphinx would also support the automatic generation of API documentation that could be included in the built documentation.