Don't call out every user in channel by name

[a13m]

When posting events to a channel, it is ugly to prefix messages with a bunch of usernames. Users can make their own decisions about whether messages from zabbirc "alert", based on the username or message content.

[mmahut]

This is probably true. At first I thought it is a good idea to use the irc names, but it is just getting messy when there is a lot of people.