fix#653
Actions Required:
* Modify calls to set the control frame callback, to
pass non-const reference instances, and manage the
lifetime of the instance.
* read and async_read now return the number of bytes inserted
into the caller's buffer.
Actions Required:
* Change the signature of completion handlers used with
websocket::stream::async_read to void(error_code, std::size_t)
Vinnie Falco