More updates for readme.txt

git-svn-id: https://plugins.svn.wordpress.org/yummly-rich-recipes/trunk@1048677 b8457f37-d9ea-0310-8a92-e5e31aec5664
Adds pixel tracker to the plugin output

git-svn-id: https://plugins.svn.wordpress.org/yummly-rich-recipes/trunk@1048680 b8457f37-d9ea-0310-8a92-e5e31aec5664