add doc link

git-svn-id: https://plugins.svn.wordpress.org/cta/trunk@871500 b8457f37-d9ea-0310-8a92-e5e31aec5664
update doc link

git-svn-id: https://plugins.svn.wordpress.org/cta/trunk@871504 b8457f37-d9ea-0310-8a92-e5e31aec5664