updated filter name

git-svn-id: https://plugins.svn.wordpress.org/edd-hide-download/trunk@841192 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated readme

git-svn-id: https://plugins.svn.wordpress.org/edd-hide-download/trunk@841194 b8457f37-d9ea-0310-8a92-e5e31aec5664