Add websocket support for attach

A new api call named "interact" has been added to ContainerManager.

It takes the same parameters as the attach call minus the callback. It returns a InteractiveStream, which is a wrapper around the "GuzzleHttp\Stream" which allows to communicate with a container (by using websocket protocol)

We can now create a container attach to stdin with a TTY and play with it: 

```php 
container = new Container([
            'Image' => 'ubuntu:precise',
            'Cmd'   => ['/bin/bash'],
            'AttachStdin'  => false,
            'AttachStdout' => true,
            'AttachStderr' => true,
            'OpenStdin'    => true,
            'Tty'          => true
        ]);

        $manager = $this->getManager();
        $manager->create($container);
        $stream = $manager->interact($container);
        $manager->start($container);
```

And now we can send command and get message: 

```
$stream->write('echo test');
$frame = $stream->receive();
echo $frame['data'];
```

Frame will have many informations (it's represent a websocket frame).

Be aware that by default this stream is blocking so if no output happens it will hang until timeout.