Clean up resource access

As a member of Code for Denver, I would like people who haven't been active in the brigade for a long time to not have access to delete everything we've done.

Let's send out a heads up first, and then clean up our access control. Anyone that is mistakenly removed as a contributor from something can reach out to us to be re-added.

I think we should be able to see last activity / log-ins in flowdock and github.

Start by reviewing the organization's current GitHub access and determining how last activity or logins can be checked in GitHub and Flowdock. Done means affected contributors receive advance notice, inactive access is cleaned up, and a way to re-add mistakenly removed contributors is established.

Written by the indexing model from the issue text.