DEV: Build wheels using cibuildwheel.

[jvkersch]

Adds a command to the README to build vpsearch wheels.

Under normal circumstances cibuildwheel is most useful when it is run automatically from within Travis or GitHub actions, so that it can build wheels for all supported Python versions and platforms. If there is interest (and if GitHub actions can be enabled on the admin side) I can set that up as well. If not, building the wheels manually for Linux also works.

[jvkersch]

Some background information, to facilitate reviewing:

1. cibuildwheel abstracts away a lot of low-level operations that otherwise require some insight into build processes on different platforms. For example, auditwheel repair (a step run after the wheel has been built) will detect that the wheel depends on an external library (Parasail), will copy that library in, and fix up rpath to point to the patched location. I've verified this on Linux but I think this also works for macOS. With some elbow grease it may be adaptable to Windows as well (e.g. sklearn has a package to do this).
2. I think the command quoted in the README only works on Linux, but I am not sure.

[jvkersch]

@rahulporuri Did you have a chance to try this out? If not let's merge this as-is -- it's just an addition to the docs anyway.

[rahulporuri]

I'll definitely review over this weekend.

[jvkersch]

Thanks @rahulporuri. I've added one further GitHub action to build wheels via GitHub actions, using cibuildwheel. This makes the job of building wheels for various Python versions/platforms really easy. The workflow currently has to be triggered manually (via the GitHub interface) and uploads an artifact with the various wheels upon successful completion.

[jvkersch]

I've updated the README to mention the build-wheels workflow.

[rahulporuri]

@jvkersch I have a bunch of comments. Apologies if I'm missing something trivial in the documentation.

[rahulporuri]

Also, it looks like the job didn't run earlier - https://github.com/enthought/vpsearch/actions/runs/1320491203. Do you want to try running it again to see whether or not the Action works as expected?

[jvkersch]

@rahulporuri Thanks for the review! I've replied to your comments -- please resolve the questions that you think have been answered, and I'd be happy to provide more input for the others.

Regarding running the action, I think we may be again in the same situation where an action contributed from a fork does not get run automatically. I will reach out to you offline about this. In the meantime, I have a different clone of the repo that I set up to develop this workflow, and where you can see the workflow in action: https://github.com/jvkersch/vpsearch-throwaway/actions/runs/1319590181.

[rahulporuri]

In the meantime, I have a different clone of the repo that I set up to develop this workflow, and where you can see the workflow in action: https://github.com/jvkersch/vpsearch-throwaway/actions/runs/1319590181.

I downloaded the artifacts from that job and everything looks good.

[rahulporuri]

LGTM

[rahulporuri]

@jvkersch you might want @mdickinson to take a look - but it's quite possible that @mdickinson doesnt have the bandwidth at the moment to review this PR.

[mdickinson]

LGTM; a couple of nitpick-level comments.

[jvkersch]

Thanks @mdickinson and @rahulporuri for the extensive comments! I think this is ready to go.