Implemented HttpAdapter with guzzle

I'm gonna add some comments to the code, would like for you guys to let me know what you think about it.
I think we might have to add a method to pipe the response body (which implements the guzzle/streams' StreamInterface to a tmpfile stream. Something along the lines of this:

```php
protected function streamToResource(StreamInterface $stream, $length = 1024)
{
    $resource = tmpfile();

    while ( ! $stream->oef()) {
        fwrite($resource, $stream->read($length));
    }

    return $resource;
}
```

Also, when the adapters the same thing as the read method does, returning an array with all the data including the stream, the Filesystem class will make sure the caching receives that.