Add support for stable MELPA packages
Created by: wasamasa
MELPA finally approached Marmalade with that feature. See this commit. I envision this as an extra keyword that only does something when specifying a MELPA recipe.
(quelpa 'magit :stable t) ; grabs stable release
(quelpa '(magit) :stable t) ; grabs stable release, too
(quelpa '(magit :hurr durr) :stable t) ; ignores it when a custom recipe is used