added check for ecom plugin plus default product card 2nd attr values

git-svn-id: https://plugins.svn.wordpress.org/nextgen-facebook/trunk@815538 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme update

git-svn-id: https://plugins.svn.wordpress.org/nextgen-facebook/trunk@815539 b8457f37-d9ea-0310-8a92-e5e31aec5664