Updating readme

git-svn-id: https://plugins.svn.wordpress.org/flexible-captcha/trunk@833945 b8457f37-d9ea-0310-8a92-e5e31aec5664
updating readme

git-svn-id: https://plugins.svn.wordpress.org/flexible-captcha/trunk@833946 b8457f37-d9ea-0310-8a92-e5e31aec5664