Formal branching practice for development

[artmg]

Hi fellow devs, I propose using a formal branching structure to make sure that we develop consistently and release when ready. I propose a fairly standard model except we should stick to dev and rc branchnames rather than develop and release, simply because this is what the upstream HA core uses.

So to get our dev branch back up to date I have checked out the master onto a new dev branch on my fork and have submitted this as a PR #16 .

Please let me know If you agree that the proposed structure works for you (and if my PR is a valid way to come back up to date) and we can merge it and I'll write this up as a Contributor's guide.

[foxy82]

Fine by me