Bring docs up to spec

[ssokolow]

Currently, the only documentation is the README.rst file, the docstrings, and some code comments.

I'd like to make the following improvements to bring the docs up to the standard I aspire to:

• Add a CONTRIBUTING.rst to the repo
• Audit the code and add more comments anywhere that the intent may still be vague
• Improve the PyPI description to better "sell the product"
  • Include the badges from the README.
  • Provide a longer, richer description on PyPI.
• Write a manual
  • Write a basic introduction and installation guide
  • Write Sphinx API docs
  • Publish the docs to ReadTheDocs and add the README badge
• Make it clear in the README and the manual that the PyPI version is the recommended form for installation and that updates are kept small so they can be released promptly.