---------------------------
Fixes:
- html parser: fix extraction of encoding from meta element
- use raw string for regex, fixes "DeprecationWarning: invalid escape
sequence \s" and others.
New features:
- include version infos into emeraldtree.__init__
Other changes:
- packaging modernized / enhanced: pyproject.toml, MANIFEST.in, setuptools-scm
- requires Python >= 3.9 now (dropped Python 2.x, removed "six")
- add github actions CI, remove travis CI config
- rst markup fixes / clean ups
- use tox for testing