Support reading configuration from pytest.ini

[khink]

I love Flake8lint.

It would be nice to also support reading config from pytest.ini (like currently from setup.cfg and tox.ini). We use pytest + https://github.com/tholo/pytest-flake8 for tests.

Example pytest.ini:

[pytest]
...
flake8-max-line-length = 119
flake8-ignore =
# missing docstrings
    D100
    D100
    D101
    D102
    D103
# blank lines after docstrings
    D204

If pytest-flake8 can read settings from setup.cfg or tox.ini it would also be helpful, i haven't figured out how. We don't use tox and don't need to, but maybe it's not too much work to just use tox.

I love Flake8lint. Thank you.