I have merged the GitHub commit status as I think that it was working OK.
I have now deployed the GitHub Hooks build trigger changes.
Build are automatically triggered for all pushes in all branches. There is a delay of 5 seconds so that multiple builds pushed in the same time will only trigger a single build for the last commit.
See this PR for details and if you want to review it :)
With this change, Buildbot should have a closer behavior to Travis-CI. That is, it will automatically start the builders and will report the build results in GitHub PR.