Version 5.1.0

This is a major release.

1. Completely overhauled the documentation. Instead of relying on a collection of loosely organized markdown files, the documentation is much more cohesive and hosted on readthedocs. It now includes a clear introduction to what RSMTool is as well as tutorials.
2. The RSMTool API is now richer and explicitly documented.
3. rsmcompare can now compare two rsmeval experiments as well as an rsmtool experiment to an rsmeval experiment.
4. Code coverage is now automatically computed as part of CI testing.
5. Expected warnings are now suppressed when running the tests.
6. Fixed several stylistic issues in the codebase raised by pep8 and pyflakes.