PyGObject CI System

[Christoph Reiter <reiter christoph gmail com>]

There is now a crude CI system for pygobject at
https://github.com/pygobject/pygobject-ci

It runs tests under Linux/Windows/macOS using different architectures and
Python versions for the master and 3.26 branch.

Rebuilds get triggered once per day using the cron feature provided by
travis/circle/appveyor or by doing manual dummy commits using the github web
interface.

There are still some issues with mainloop related tests failing on macOS using
travis-ci which work locally and are thus disabled (might be homebrew vs
jhbuild), but it should make it easier to spot regressions either way.

If anyone has any ideas for improving the testing etc in any way please open
an issue there :)