Remove old build results.
Pop BUILDBOT_CONFIG so it doesn't leak to subprocesses or logs.
Misc cleanup.
Periodic doesn't support codebases, so set it by hand.
Merge pull request #18 from ClusterHQ/remove-old-results

Periodicly remove old build results.
Slightly more detail on what updating is
Fixed a link
Addressed some issues from #16
Fixed a link
Add security-group image
Merge pull request #19 from ClusterHQ/improve-readme-10

Improve readme.