Introduce GitHub actions + Remove Travis CI

[Code0x58]

What does this pull request do?

this builds on @shogo82148's #376 ("introduce GitHub Actions") for #373 by increasing the range of versions tested and adding a linting stage to reflect what was in TravisCI config.

I've tested this on my own fork and it passes [actions page]

Notes:

• 1.9+1.10 skipped as they broke on ubuntu+macos with "kqueue.go:18:2: cannot find package "golang.org/x/sys/unix" in any of:" - I assume gomod related and reasonable to skip (Travis CI did run with these back in the day)
• currently failures in the lint job in golangci-lint are are allowed, to avoid making changes to the code

[nathany]

Awesome. Thanks so much for doing this!