Moved OS-specific logic to functions:
 - `find_ruby`: returns (via echo) Ruby that can be used
 - `usable_ruby`: checks whether Ruby satisfies Homebrew

Pre-create OS-specific error messages:
 - `upgrade_fail`: message that is printed when Homebrew fails to upgrade
   vendor Ruby
 - `install_fail`: message that is printed when Homebrew fails to install
   vendor Ruby

Unconditionally set `TERMINFO_DIRS` when installing/upgrading vendor Ruby
**but** export it on Linux only.

Motivation: move OS-specific logic to functions so that it's easier to
understand the main steps.

Add missing `help` methods for external `cask` commands.

Use `CLI::Parser` for `cask` commands.

Allow iOS and iPhone at the beginning of descriptions.

GitHub Actions cleanup

- Add consistent spacing
- Remove `pull_request: []` warning
- remove identical, implicit `name` usage
- use `actions/cache@v1` for compatibility

tests.yml: minor tweaks

docs: update GitHub rate limit URL

audit: check GitHub tags for prerelease status

Add `cask-eid` to list of deprecated taps.

utils/ruby.sh: test_ruby(): keep temporary variables local

version: add major, minor, patch methods

rubocop/urls: add go@1.14 to binary URLs allowlist

workflows: test on "push" not "pull_request".

cleanup: fix input handling

Co-authored-by: Mike McQuaid <mike@mikemcquaid.com>

Add xonsh update-python-resources blocklist

build(deps): bump html-pipeline from 2.13.0 to 2.14.0 in /docs

vendor/bundle/ruby: unvendor REXML

.gitignore: correct mechanize ignore matching

os/mac/system_config: simplify JVM version parsing

download_strategy: more direct SVN modified date detection

utils/github: add check_for_duplicate_pull_requests

Moved from dev-cmd/bump-formula-pr to utils/github

Fix `Desc` cop for casks.

Co-authored-by: Bo Anderson <mail@boanderson.me>

Fix auditing of cask languages.