[ANN] New Clojars feature: removing users from groups

[Toby Crawley]

We've just deployed an update to Clojars that allows you to remove
users from groups. Before now, doing so required having one of the
Clojars administrators do it for you.

It works like this:

* Group membership now has an admin flag associated with it
* Group admins can add members, promote members to admins, and demote
admins to members
* A user cannot alter his/her own admin status

For existing groups, we tried to make sure at least one user had admin
rights, but there are cases where more than one user was made admin,
and possibly a few cases where no one was made admin. The algorithm we
used to determine initial admin rights was based on the who added the
user to the group - if that value was "clojars" (meaning the user
created the group) or null (meaning the user was added to the group
before January 2013, before we started tracking the provenance of
membership, and therefore can't determine the creator), admin rights
were given.

If you have a group that has no admin, or the admin we selected is no
longer involved with the group, please file an issue at
https://github.com/clojars/clojars-web/issues and we'll sort it
out. Also please file an issue if you run into any problems with these
new features.

We want to thank Marcelo Nomoto for implementing this feature, and
seeing it to completion over several rounds of PR review.

- The Clojars Team