New command

Since I am encountering firewall problem which does not allow incoming connection, BTQueue looks so slow comparing to firewall which did not allow outgoing connection. To solve this problem, I guessed BT protocol implemented in BitTornado might have done something weird that make it act like that. So, I defined new command named "last_message" for verifying protocol interaction between BTQueue and other peers. In addition, you can set MAX_LAST_MESSAGE using gset command to specify number of messages kept in queue.