[Checkins] [zopefoundation/BTrees] d1e1f8: Add documentation for the unsigned modules.

[Jason Madden]

  Branch: refs/heads/issue120
  Home:   https://github.com/zopefoundation/BTrees
  Commit: d1e1f8792ca83379f0ad47d42ecc8b266767d55a
      https://github.com/zopefoundation/BTrees/commit/d1e1f8792ca83379f0ad47d42ecc8b266767d55a
  Author: Jason Madden <jamadden at gmail.com>
  Date:   2020-02-17 (Mon, 17 Feb 2020)

  Changed paths:
    M BTrees/BTreeModuleTemplate.c
    M BTrees/SetTemplate.c
    M BTrees/__init__.py
    M doc-requirements.txt
    A docs/_static/custom.css
    M docs/api.rst
    M docs/conf.py
    M docs/index.rst
    M docs/overview.rst

  Log Message:
  -----------
  Add documentation for the unsigned modules.

And some other small tweaks to the documentation to make cross-references work and things generally look good.