Add support for configuration inside 'setup.cfg'

[althonos]

While I am at it, I added support for green configuration inside setup.cfg, since there seem to be an almost official agreement about using this file for Python dev tools configuration.

setup.cfg is the only file where the [green] section is expected.

[coveralls]

Coverage remained the same at 100.0% when pulling 70488cc8dae59b419482ea3518499976db87238e on althonos:feat-setupcfg into 8a7a0bdefc2ed7f2ad1121cff12e967ae0017924 on CleanCut:master.

[coveralls]

Coverage remained the same at 100.0% when pulling 70488cc8dae59b419482ea3518499976db87238e on althonos:feat-setupcfg into 8a7a0bdefc2ed7f2ad1121cff12e967ae0017924 on CleanCut:master.

[CleanCut]

Also...I wonder if we should change our config-file resolution behavior from merge-all to "first config wins..." Something to ponder.

[CleanCut]

I've been pondering it. I like the current merging-of-configs behavior, I think.

By the way, if you feel like you need some help with my review suggestions, let me know and (I think) I can make a PR to your PR adding some of the stuff. If that helps.

[althonos]

Merging is okay, this allows changing some things locally while having a global configuration that is used everywhere, both of which can be updated independantly.

I do not agree with setup.cfg being the least in priority however, since it is a local configuration file (at the root of a Python project): it should have precedence over the global settings, as the .green file does.

EDIT: Oh, I see what you mean, not absolute first but just come before .green.

[coveralls]

Coverage remained the same at 100.0% when pulling 2379baa2e2b5533b415414887361d219552594e2 on althonos:feat-setupcfg into 8a7a0bdefc2ed7f2ad1121cff12e967ae0017924 on CleanCut:master.

[CleanCut]

Yes, I meant switch it with .green. Sorry, I could have explained that more clearly.

[CleanCut]

Included in just-released version 2.9.0.