edited readme.txt

git-svn-id: https://plugins.svn.wordpress.org/custom-content-shortcode/trunk@782297 b8457f37-d9ea-0310-8a92-e5e31aec5664
edited readme.txt

git-svn-id: https://plugins.svn.wordpress.org/custom-content-shortcode/trunk@782299 b8457f37-d9ea-0310-8a92-e5e31aec5664