Update compatibility with version 4.0

git-svn-id: https://plugins.svn.wordpress.org/commercekit/trunk@979040 b8457f37-d9ea-0310-8a92-e5e31aec5664
Correct stable version

git-svn-id: https://plugins.svn.wordpress.org/commercekit/trunk@979048 b8457f37-d9ea-0310-8a92-e5e31aec5664