Maintain '*-stable' branches

[pathawks]

This is very much wishful thinking

When I merge a pull request with @jekyllbot: merge +bug it would be cool if, in addition to merging into master @jekyllbot could cherry-pick the merge commit into the appropriate *-stable branch and update History.markdown in that branch. That way, I would never have to deal with manually backporting, but could just cut a release from that branch and trust that it has all the latest bug fixes already.