I have developed a simple WordPress plugin to add active class to menu item li tag. Currently it is current-menu-item or current_page_parent. You can even set custom class to li tag if your need is other than active class. Hope you will like it.
Download it from: https://wordpress.org/plugins/wp-add-active-class-to-menu-item/
Note: For any customization or help please do contact me on my mail or at plugins support page.