What does this repo do? Please improve the readme

[cthoyt]

It's not clear from the README of this repo (nor the PyPI page) what this repo is for. The readme should have some examples of use cases/examples so people know if this is the right repo or something like pronto, obonet, nxontology, pyobo, etc. are better suited. I see there's a link to documentation on readthedocs, but this also assumes a potential user will be willing to go through the documentation enough to find examples (again, there are no examples on the landing page of the docs)