Ratchet SessionProvider with WampServer Error
I am having a hard time getting the SessionProvider to work with my current Ratchet server implementation.  I am currently using Ratchet 0.4

server.php
```php
$loop   = React\EventLoop\Factory::create();
$pusher = new MyApp\Pusher;

$context = new React\ZMQ\Context($loop);
$pull = $context->getSocket(ZMQ::SOCKET_PULL);
$pull->bind('tcp://127.0.0.1:5555'); 
$pull->on('message', array($pusher, 'onBlogEntry'));

$webSock = new React\Socket\Server('tcp://127.0.0.1:port',$loop);

$memcache = new Memcache;
$memcache->connect($ip, $port);

$webServer = new Ratchet\Server\IoServer(
    new \Ratchet\Http\HttpServer(
        new Ratchet\WebSocket\WsServer(
            new Ratchet\Session\SessionProvider(
                new Ratchet\Wamp\WampServer(
                    $pusher
                ),
                new Handler\MemcacheSessionHandler($memcache)
            )
        )
    ),
    $webSock
);

$loop->run();
```

I continue to get an error: 
```
PHP Fatal error:  Uncaught TypeError: Argument 1 passed to Ratchet\Session\SessionProvider::__construct() must implement interface Ratchet\Http\HttpServerInterface, instance of Ratchet\Wamp\WampServer given, called in push-server.php on line 28 and defined in cboden/ratchet/src/Ratchet/Session/SessionProvider.php:47
```

I have tried several different implementations, but based on the documentation 
[here](http://socketo.me/docs/sessions) the SessionProvider should be able to wrap the WampServer, however this does not seem to be the case as the WampServer does not implement the HttpServerInterface. 

Is there something I am missing to use the SessionProvider wrapping a WampServer? 