'tell' command added

-'tell' command added.  'tell' allows a player to send a message to
another player, and no one else, by using 'tell <player_name> <message'.
-the apostrophe (') command now intelligently either chats, or responds
to the last person who sent you a tell, if they are still on.  If they
are no longer on, the server sends a message saying that, and then the
apostrophe command will chat once again.