Fixes incorrectly exiting when user QUITs

Only respond to QUIT messages that have a matching username to the
logged in user, instead of any QUIT messsage

main.go

@@ -79,7 +79,7 @@ func main() {
 		if message == nil {
 			continue
 		}
-		if message.Command == irc.QUIT {
+		if message.Command == irc.QUIT && message.Prefix.Name == config.Nick {
 			log.Printf("Server sent QUIT, exiting")
 			running = false
 			//Exit with a non-zero status so the system process restarts this process