Determine appropriate use of usage.rst

Determine the appropriate use of usage.rst. If the file is to be used by those who are contributing, should this file be a .rst file along with the rest of the docs? If this is merely for developers, does it make more sense to move it to the root of the file structure and change to markdown to be more GitHub-viewing-friendly?

Start by reading usage.rst and the repository's Sphinx documentation structure. Determine whether the file serves contributors or developers, then establish whether it belongs with the .rst docs or at the repository root as Markdown; done means its audience, location, and format have been decided.

Written by the indexing model from the issue text.