[Dovecot-news] Dovecot code repository moved to Github

http://hg.dovecot.org/ is no longer being updated. The public repository exists now in https://github.com/dovecot/core instead. I'm not sure yet if we should continue pushing commit emails to dovecot-cvs list or if Github's internal notifications are enough. In any case dovecot-cvs list isn't working right now.