use the release branch for docs releases too - that way its always ready...

... for the next patch release

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@docker.com> (github: SvenDowideit)

Simplify the documentation and patch release process by getting the docs team to release their out of band updates to the docs site from the same release branch.

> **Warning:**
> This changes to the current `release` branch
> 1. It makes the `release` branch a living thing - ideally, simple docs PR's would be merged from master many times a day, and published from the `release` branch automatically
> 2. It cherry-picks the __merge__ commit, and rolls the changes into that commit. This allows the `pulls compare` code to track the differences between the master and release branch, and simplifies the cherry-pick process.