py2/py3 compatbility release, adds support for python3.9

convert to face CLI frameworkg

the accurate version is the best version

upgrade dependencies and release a real (calver) major version

tweaked anchor generation to use dashes and add rel=noopener for exte…

…rnal links

link retargeting and a few dependency bumps

lots of small fixes, robustness improvements, and logging sync up wit…

…h lithoxyl

fixed and improved feed html with table of contents and better canoni…

…cal linking

fix some packaging snafus caused by a stray site directory being pack…

…aged

the biggest change is the new part-based format, but also many fixes …

…and improvements, too many to list in the tag message, see the commit log for details