Readthedocs support

We'd like to set up a Read the Docs instance for all Pylons Projects github-hosted projects (Pyramid, Pylons, all Pyramid add-ons, all Pylons project libriaries such as Colander and Deform). The system should have the following features:

• If we choose to run our own RTD instance, we should create a buildout for it.

• Get all docs under Pylons Project namespace

• Point out docs.pylonsproject.org to the namespace

• Should show docs for all existing tags for each package.

• Automatically publish new revision of docs when a tag is made to git

• Automatically update a dev version of the docs for each package every X minutes