Websocket url must not be handled as regular request, the response depends on handshake completion

Previously, we handle handshake and request on the same response, this is not compliant with the specification, and may annoy browsers.
Now handshake requests are not serving resources anymore, but write the response as soon as the handshake is completed (successfully or not).

Signed-off-by: Clement Escoffier <clement.escoffier@gmail.com>
Fix issue #56

Signed-off-by: Clement Escoffier <clement.escoffier@gmail.com>