Update and fix Continuous Integration

[geographika]

Appveyor appeared to have an issue running pytest directly for Python 3.7 and above (and pytest v7+).
Fixed by changing to python -m pytest

Also deprecation warnings for using hyphens in setup.cfg. description-file changed to description_file to fix this one (underscores are fine).

Removed Travis CI from repo and replaced with GitHub actions. See https://github.com/actions/setup-python

This was mostly fine, except for trying to migrate coveralls and setting up https://coveralls.io/github/geographika/mappyfile
pytest-cov does not output lcov files, which are the only format which work with the "official" coverallsapp GHA:

coverallsapp/github-action#30 Can I use only LCOV files? #30

Had to try various options and settings before getting it working, and having to exclude Python 2.7
Various links that were useful (and confusing at the same time):

• https://stackoverflow.com/questions/60910770/python-project-code-coverage-badge-with-coveralls-github-actions
• https://coveralls-python.readthedocs.io/en/latest/usage/configuration.html#github-actions-support
• https://github.com/TheKevJames/coveralls-python
• Github Actions raises a 422 error TheKevJames/coveralls-python#252

Also setup.py is now deprecated for building wheels etc.
See https://blog.ganssle.io/articles/2021/10/setup-py-deprecated.html
Used pip to install https://pypa-build.readthedocs.io/en/stable

Read the docs also was deprecated: http://docs.readthedocs.io/en/latest/yaml-config.html
Switched to https://docs.readthedocs.io/en/stable/config-file/v2.html