Be more specific in printed output

* Say whether we are Installing, Upgrading, or Skipping.
* Changes the behavior of `brew_install_or_upgrade`
 but simplifies and shortens the rest of the script.
The quotes are optional on all of these. How do we feel about instead saying e.g.

    brew_install_or_upgrade reattach-to-user-namespace
    brew_install_or_upgrade gh