Not working on images with srcset attribute

The plugin works well, but only on images that don’t have the srcset attribute.

The issue is solved by renaming the srcset attribute to data-srcset, as the a3 Lazy Load plugin does.

Here is a quick, but not very elegant solution. Apply the following patch on the speed-up-lazy-load.php file:

165a166,167
>         $append = preg_replace('# srcset="([^"]+)"#', ' data-srcset="\1"', $append);
>