Changing the way an attach response is read

This PR fix a problem with readAttach which was not working.

Actually we use fgets and a payload for readAttach, this cause problem as it bufferize the stream and remove some caracters. 

To fix this i remove the readAttach method and create a new AttachResponse which is used when we detect a specific content type for the Response.
The attach response has its own method to read a line from the stream.

Due to this change, i also rework how the callback must be set. All callback pass to the read method can now have the following signature : 

```
function ($output, $type) {

}
```

In case of an attach call $type will be set, in other case it will be null. Older callback with only $output will work. This also cause that the callback pass to run method in ContainerManager have to respect this signature (order of $output and $type parameters was inversed in the old callback)