Revise documentation

[mphoward]

This is a new issue (building from #1) to track edits and revisions that need to be made to the documentation:

• [ ] Main index should either embed the readme or have some text included
• [ ] Installation instructions need to be condensed (borrow from readme). The tutorial text that is there is for verifying an installation.
• [ ] Add module level documentation for pretty much all modules.
• [ ] Add overview text for Potentials index page (in addition to toc).
• [ ] Math equations are rather broken, try to clean them up.
• [ ] Check for use of single vs. double ticks throughout.
• [ ] Collapse release notes table of contents by adding a v0.x header. This will be useful when we finally get to v1.0.0.
• [ ] Check tutorials for typos. At least one of them is misnumbered since there are two "Tutorial 3". I would propose that we actually get these separated out into individual directories (do not include two related notebooks in one folder) to make it easier to count them.
• [ ] Proofread all modules.
• [ ] Remove test version of HOOMD from README. It is easy to let it get out of date.
• [ ] Add badge to README for RTD.
• [ ] Check for missing :members: documentation where it's needed.

Anyone should feel free to work on these. Please document on this thread if you complete an item, especially if you proofread a module.

[astatt]

Do you want to address these points in a separate branch or as hotfixes?

[mphoward]

They can be addressed whenever we feel like it, in any size chunk, and merged immediately to main. (I am going to remove the develop branch after we merge the last open PRs.)

[astatt]

There is a typo in the equation for the spline pair potential -- it should be a*(r_cut2-r2)m*(r_cut*2+mr2-(m+1)*r_s2)/(r_cut2-r_s2)(m+1)

[mphoward]

The documentation will need to be redone when v1 is ready.