updating readme.txt

git-svn-id: https://plugins.svn.wordpress.org/generic-affiliate-system-for-marketpress-or-woo-commerce/trunk@796310 b8457f37-d9ea-0310-8a92-e5e31aec5664
updating documentation at readme.txt

git-svn-id: https://plugins.svn.wordpress.org/generic-affiliate-system-for-marketpress-or-woo-commerce/trunk@796311 b8457f37-d9ea-0310-8a92-e5e31aec5664