Remove some deprecated constructs

Clean up some now unused code and clean up deprecated constructs,
including splitting of pytest.Item and pytest.Collector (pytest.File)
and using pathlib.Path a bit more.

Bump version

Fix some typos; from @kianmeng
Bump version for new release

Bump version

Add a few fixes required by latest python and/or pytest, as well as
documenting some behavior that may be unexpected (skipping tests when no
changes).

Bump version

With flake8 compatibility fixes, bump version accordingly.

Make this properly build, and test on Python 3.8

from_parent() will only take 2 arguments, so make the rest optional
when setting them manually.

Also add Python 3.8 to platforms we run tests on.

Bump version.

- Support flake8 3.7+ by checking existence of "app.make_notifier";

  from jirikuncar@github
- More fixes for Travis CI -- properly specify Python versions, in
  particular for pypy (and fix a typo)

- Don't use long deprecated functions from pytest, broke with pytest …

…4.1.0

- Fix typo that caused some tests to not run as expected
- Run Travis CI tests against Python 3.7, and fix some issues with current tox

- Test on Python 3.7

- Escape a regex tring with r""

Address a change in pytest 3.5.x on junit node identifiers.

- Honor ignore settings in default flake8 config section; from

  brianbruggeman@github
- Improve junit XML output; from Struan Judd
- Fix test conditions to work better with current pytest