1.51 updated readme

git-svn-id: https://plugins.svn.wordpress.org/shortcode-exec-php/trunk@883179 b8457f37-d9ea-0310-8a92-e5e31aec5664
1.51 updated readme

git-svn-id: https://plugins.svn.wordpress.org/shortcode-exec-php/trunk@883180 b8457f37-d9ea-0310-8a92-e5e31aec5664