IRCContact use the DATA API

IRCContact consume 2 events:
 1. ('builders', None, 'builds', None, 'new') => A build is started
 2. ('builders', None, 'builds', None, 'finished') => A build is finished

When we will be able to get the list of changes for a build, the IRCContact must be updated.
What about parameter `tags`?  It's not used, is it?