The setup.py test command and pytest-runner have been deprecated for
several years and are no longer recommended. The pytest documentation
no longer recommends pytest-runner and their own documentation
recommends against it.

- https://github.com/pypa/setuptools/issues/1684
- https://github.com/pytest-dev/pytest/issues/5534
- https://github.com/pytest-dev/pytest-runner/issues/50

Changes made:

- Removed pytest-runner: Eliminated the use of pytest-runner from
  `setup.py`.
- Moved test dependencies to the `extra-dependencies`, which can be used
  by tox as well as for manual installation.
- Updated the documentation to recommend using tox as the default test
  runner. Alternatively, users can manually run tests with the `py.test`
  command.

These changes will also make an eventual migration to `pyproject.toml`
easier, as the `extras_require` can be copied to the
`project.optional-dependencies` section.

This is based on
https://packaging.python.org/en/latest/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows/#defining-a-workflow-job-environment
. It's the sample config from there, with versions updated and
our project name substituted in the appropriate places. I dropped
the publish-to-testpypi bit because of
https://github.com/pypa/packaging.python.org/issues/804

 , and left
the Github release part left out for now. We can add that later if
we like, but we never published releases to Github before, so it
doesn't seem required yet. I also tweaked the conditionals a bit
to avoid running the build job on forks and publish only tags
that start with 'v', as that's our convention for versions.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

It's much nicer to have the main repo as origin and your fork as
another remote you just push PR branches to. That way you don't
have to deal with resyncing the master branch of your fork all
the time.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

Per #223

Per #223

We switched to pycodestyle then flake8 recently, but one stray
reference to pep8 was left in this doc file.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

somtimes -> sometimes
if do -> if you do