Added callback to poll on getMessage

Added announcementCallback function to poll on getMessage() every
1000ms. This function then passes the received data on to playTurn().
Added playTurn() logic to handle the various announcement types. Right
now it will move a player and add text to the chat room. Added NOP
announcement type in the event that the game server player queue is
empty. Added A_CHAT action type so players can message each other in the
chat room. Improved the way getMessage handles and returns the received
message from the server.