PR: Move CI to Github Actions

[goanpeca]

@ccordoba12 I added as much options as possible with github actions.

Which versions should we test for python and which builds could we skip?

It is still pretty fast with the current setup.

[ccordoba12]

Which versions should we test for python and which builds could we skip?

I think Python 2.7, 3.7 and 3.8 should be fine.

[goanpeca]

@ccordoba12 I suggest we use the oldest version we support and the newest, since older version are more likely to produce "issues", in that case, would that be

2.7 3.6 and 3.8?

Or are we officially supporting 3.5 ?

[CAM-Gerlach]

@ccordoba12 Any insight on why the CIs were disabled? It seems this project has gone essentially unmaintained for the past year, despite substantial community interest and it being in the top 200 packages on PyPI... I'll do my best to put out some fires where I can.

[CAM-Gerlach]

@ccordoba12 I had to fix a number of outstanding and accumulated issues with it, update it to the latest versions of the relevant deps and fix some sub-optimal practices, rebase and clean up the commit history, update the relevant metadata and make some other improvements, but this should be all good to merge now.

Most notably, because the Qt4 packages appear to no longer be available on either pip or conda for any supported platform or channel, I had to drop those tests, though otherwise support for Qt4 itself is not officially dropped anywhere other than the CI tests. However, we should consider perhaps cutting a 1.10 release with these changes, updated metadata and the other pending PRs, and then a 2.0 release with support for Qt4 and Python 2.7 dropped (since we are no longer able to test that platform, and Python 2.7 has been EoL for over a year).

[CAM-Gerlach]

With my plethora of fixes, LGTM now.

[CAM-Gerlach]

@ccordoba12 gave the okay to go ahead with this, so I'll merge this now to get our CIs working and unblock the other PRs