Unify documentation

[amc-corey-cox]

Glass pointed out that there is potentially a fair amount of duplication in our documentation now with the README.md and CONTRIBUTING.md rewrite and overlap with the online documentation. I think it is valuable to have our documentation available in both places.

However, it would be a good idea to unify this overlapping documentation. We should investigate if there is a way to manage the documentation in one location and generate documentation as we want.