Hey Aaron, great plugin. Thanks.

I have suggestion: keep parent and ancestor classes. They’re very useful for sites with many pages and when you need to highlight or hide some .

Maybe you could change the nav_class_filter.

Before:
return is_array($var) ? array_intersect($var, array('current-menu-item')) : '';

After:
return is_array($var) ? array_intersect($var, array('current-menu-item', 'current-page-ancestor', 'current-page-parent')) : '';