Add a pre_fire_hook callback to fedmsg.publish.
Add a pre_fire_hook callback to fedmsg.publish.

This can be extended by other libraries to do something before publishing.

cicku/fedmsg,chaiku/fedmsg,vivekanand1101/fedmsg,maxamillion/fedmsg,pombredanne/fedmsg,fedora-infra/fedmsg,vivekanand1101/fedmsg,cicku/fedmsg,maxamillion/fedmsg,pombredanne/fedmsg,pombredanne/fedmsg,fedora-infra/fedmsg,fedora-infra/fedmsg,chaiku/fedmsg,maxamillion/fedmsg,cicku/fedmsg,vivekanand1101/fedmsg,chaiku/fedmsg