* Needed a hook to call on_close so we could execute logic when a
  connection is closed from the client end.
* Websocket close failed if we didn't pass through an integer status
  code, so added defaults to send this if not present. This behaviour is
  probably wrong for non-websocket clients

This version breaks with IE 10

Faye::Websocket response objects, don't have a finish method, so
currently if we reach the close method inside a Consumer from a
websocket connection, the server will force exit.

Figuring out why there is this discrepency would require some heavy duty
archaeology into the codebase, but I'm not sure it's worth it just now.
This fix just prevents us trying to call finish on an object that
doesn't respond to it.

Attempt to encode strings as valid UTF-8 before we do the gsub
replacement into the string, as this just breaks if passed invalid
UTF-8.

This is what Safari uses, and it seems unable to connect to the server
without this header in the response.

Several major/minor bug fixes

Let's not crash if passed invalid utf-8 strings.

Let ruby determine the input encoding