Call to undefined method React\HttpClient\ChunkedStreamDecoder::end()

Hello,

I encountered the following error using the react http client (v0.4.11) : 

```
Call to undefined method React\HttpClient\ChunkedStreamDecoder::end()
```

Indeed in Response.php it seem that `$this->stream->end()`is not (always?) resolved

Fixed my issue by getting back to 0.4.10.

Cheers.
