* Tested with WordPress 4.7.1
* Tested with WooCommerce 2.16.12.
* New feature added: exclude group members from using coupons.
* Updated and improved the coupon user interface related to groups.
* Added a readme.txt to the plugin's root folder.
* Fixed a potential warning issued when a coupon is not valid and has
no groups assigned.
* Improved internal checks that decide whether to show the error message
for coupons restricted to group members.
* Added the plugin's translation template.
* Added the German translation.
