Ensuring that WebSocketConnection#disconnect sends appropriate message on close.

Ensuring that WebSocketConnection#disconnect sends ConnectionHandler#CLOSE_NORMAL instead of ConnectionHandler#CLOSE_CONNECTION when the client explicitly closes the connection.

On a side note, why are the close constants in WebSocket.ConnectionHandler different from those specified for the WebSocket Protocol - http://tools.ietf.org/html/rfc6455#section-7.4
It seems to me that it would clarify and simplify Autobahn if it were to use the protocol close constants.