Use Github Actions

[curiositycasualty]

This mainly does 2 things:

• swaps to Github Actions for CI (instead of travis) and
• gussies up the existing formulae to meet brew style and brew audit standards

If brew style and brew audit are good enough for homebrew-core, they're good enough for your tap.

[curiositycasualty]

Looks like I've got something to fix with regards to the resty CLI. Please stand by.

[curiositycasualty]

Took me way too long to figure out that converting the openresty formulae to keg-only (as brew style --fix stipulated), causes the symlinks for the resty/nginx binaries to NOT be created as they were previously. This led to the formulae installing successfully, but is causing the kong CLI tool to fail:

env: resty: No such file or directory
Error: Process completed with exit code 127.

As seen here: https://github.com/Kong/homebrew-kong/runs/4537975626?check_suite_focus=true#step:12:5374

This log message when installing openresty directly tipped me off:

==> Caveats
openresty@1.19.3.2 is keg-only, which means it was not symlinked into /usr/local,
because this is an alternate version of another formula.

If you need to have openresty@1.19.3.2 first in your PATH, run:
  echo 'export PATH="/usr/local/opt/openresty@1.19.3.2/bin:$PATH"' >> ~/.zshrc

Let me figure out if there is either a way to not need to be keg-only without pissing off brew style, or if there is a way to force the binary installs for keg-only fomulae.