Host multiple versions of the documentation.

[curtisma]

Problem Statement

We are currently only hosting the documentation for the most recent version of virtue. However if a user is still using a previous version of virtue in their project they may want to consult the docs for that version.

Proposed Solution

We will move our documentation to be hosted on ReadTheDocs (RTD) rather than GitHub. RTD should be able to build and host the docs for free. We can even use it with our custom domain name.

Then different versions of the docs can be selected easily using a drop-down provided by the pydata theme:

Alternatives Considered

Proposed Action Plan

We should start by following the tutorial:
https://docs.readthedocs.io/en/stable/tutorial/

I'm sure the conf.py will need to be updated.

• 1. we'll do this
• 2. We'll do that
• 3. Then we'll add tests for this and that.