Hi Frank,
Thanks for such an awesome plugin. I am sure next version is going to be great too.
Just a suggestion from my side. I analyzed this behavior of HTML optimization in GTMetrix in which it removes quotes from single string attribute values. For this purpose I created a regular expression, maybe you can add it in the next version.
preg_replace("/([\"\'](?=[a-zA-Z0-9\-]*[\"\'][^>]*>))([a-zA-Z0-9\-]+)\\1/", '$2', $content);
I know it won’t affect much, but I was getting too obsessed with getting a 100% rating (LOL)