def set_topic(topic)
      room.update("topic" => topic) do
        room.topic = topic
        client.numeric_reply :rpl_topic, channel, ':' + room.topic
      end
    end
def set_topic(topic)
      room.update("topic" => topic) do
        room.topic = topic
        client.numeric_reply :rpl_topic, channel, ':' + room.topic
      end
    end
Public: set the topic of the campfire room to the given string
 and lets the irc client know about the change

 topic - the new topic