It’s working now.
Thank you for fast response and for an awesome plugin!
I think you missed one more at template-functions.php:105.
Unfortunately, I cannot provide the link since I am testing on local machine.
But here is the error from the debug.log: http://pastebin.com/11YnSCRN.
The reason seems to be that wp_make_content_images_responsive() was introduced in WP4.4 .
