Update Readme

git-svn-id: https://plugins.svn.wordpress.org/wordpress-ecommerce/trunk@873031 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fix youtub elinak in readme

git-svn-id: https://plugins.svn.wordpress.org/wordpress-ecommerce/trunk@873033 b8457f37-d9ea-0310-8a92-e5e31aec5664