Set up CI

[mathstuf]

This crate is currently missing CI. Given its multi-platform code, most contributors aren't going to be able to test all of them easily, so CI should do it for folks.

Cc: @Minoru

[Minoru]

Travis config uploads docs somewhere. The README only links to docs.rs, so perhaps this could be dropped? Everything else is trivial enough to port to GitHub Actions. I'll work on that right now.

Windows builds on AppVeyor stopped for no apparent reason. I think they can be moved to GitHub Actions as well, but I won't take this upon myself.

[Minoru]

#28 migrates the Linux jobs.

macOS jobs occasionally fail the smoke test: https://github.com/Minoru/wait-timeout/runs/2843431331?check_suite_focus=true That happened to 2 runs out of 3. I don't have a macOS machine to investigate, so I left that out.

I also attempted to migrate Windows to GHA. It mostly works, but i686-pc-windows-gnu target fails to find a linker: https://github.com/Minoru/wait-timeout/runs/2843383677?check_suite_focus=true I think we need to install wingw to fix that, but again — i don't have a machine to test, so I left that out as well.

[mathstuf]

I think we can probably ignore 32bit windows for now if 64bit works.

[Minoru]

Okay, so the three Linux jobs and the x86_64-pc-windows-msvc job are in CI now. What's left to do in this issue:

• fix the occasionally failing smoke test on macOS, and add it to CI
• (optional) add more Windows targets to match what we had in AppVeyor

[mathstuf]

Thanks. I'll try and poke about on the Apple hardware I have access to, but I don't have a timeline.