Re-add homebrew/Qo, homebrew/Rs

[icy]

which are removed from #171

[icy]

Rel. : #170

[icy]

I'm not really interested in implementing some backend's feature. This would be something needed to be done by homebrew. Let me dig in their issues system and docs.

[icy]

On Ro: https://superuser.com/questions/781693/how-to-determine-which-brew-package-provides-a-given-file

[rami3l]

@icy AFAIK homebrew has added brew autoremove [--dry-run], but this doesn't accept parameters (yet).