Use an active fedmsg socket instead of passive ones.

This will cause trac to call out to an instance of fedmsg-relay running
somewhere.

This is preferable over binding to our own sockets because trac's
component management system re-instantiates our plugin for every http
request (I didn't think it did that before...).
Merge pull request #2 from fedora-infra/feature/active-instead-of-passive

Use an active fedmsg socket instead of passive ones.
Merge branch 'release/0.2.0' into develop
Merge branch 'develop' of github.com:fedora-infra/trac-fedmsg-plugin into develop
0.3.0
Merge branch 'release/0.3.0'