cibuildwheel

[snowman2]

This was brought up in #73 by @vincentsarago. I didn't want to go through the headache of transitioning from multi-build for pyproj. But, after troubles with multi-build, I decided to give it a try and am happy with it so far. I added reference to the PRs in case this becomes something you want to try.

Reference implementation:

• CI: Use cibuildwheel for OSX pyproj4/pyproj#1042
• CI: cibuildwheel linux pyproj4/pyproj#1046

[sgillies]

@snowman2 I almost feel like I could do this now that we've figured out how vcpkg manifests work. It would be nice to have just one wheel building framework.

GDAL is more complicated than PROJ, though. We'd need to do some checking that all its vcpkg dependencies are good enough. Yes, we've been using vcpkg for Windows and haven't had big complaints, but most of our users, and all of our "power users", are on MacOS or running in "the cloud" on Linux.