v0.19

  [AE::WS::Connection enhacements (thanks Toshio Ito)]
  - Automatically respond to a close frame with a close frame (RFC6455 5.5.1)
  - Make sure "finish" callbacks are called only once.
  - Automatically shutdown the socket on "finish" event. This makes sure EOF signal is sent to the peer.
  - Refuse to send/receive frames after it sends/receives a close frame. (RFC6455 1.4, 5.5.1)
  - Abort the connection when it receives a too huge message. The size limit is imposed by Protocol::WebSocket::Frame (RFC6455 10.4)
  - Automatically respond to a ping frame with a pong frame of the same payload (RFC6455 5.5.2, 5.5.3)
  - Add "masked" attribute. If set, outgoing frames are masked.
  - Client's Connection now sets masked => true (RFC6455 5.3, 6.1).
  - documentation