Add AArch64 wheel support

[odidev]

Closes #221

@chriskuehl, can you please take a look into it? Thanks in advance !

[chriskuehl]

I was a bit confused by this line:

docker run --rm --privileged hypriot/qemu-register

At first glance this seems like it "should" have no effect, but looking at the image itself, it looks like it's basically relying on kernel side effects: https://github.com/hypriot/qemu-register/blob/85e908922d09bfe3f6b6144da7d9c09ff880744e/register.sh. Unfortunately we won't be able to support this on the build machines we're using for this project's releases.

I'm happy to add aarch64 wheels but we would need to do it through Travis CI (rather than QEMU) like we are currently for the other non-amd64 builds.

[odidev]

Travis CI is paid now. How about using CircleCI? It is free and offers AArch64 build agents as well. Please let me know your thoughts here?

[odidev]

@chriskuehl, can you please let me know your thought on this

[chriskuehl]

@odidev I just merged #257 which switches us over to GitHub Actions for CI, using QEMU for the non-native builds. I think it should be pretty easy to start building Python wheels now, we just need to parameterize the manylinux1 Docker image and add make python-dists as another build step (or something like that). Then we would expose those as build artifacts (the same way we do for the Debian package and executable).

[chriskuehl]

Closing this in favor of #258