Readme fixed.

git-svn-id: https://plugins.svn.wordpress.org/cleantalk-spam-protect/trunk@789280 b8457f37-d9ea-0310-8a92-e5e31aec5664
Tested with WP 3.7.

git-svn-id: https://plugins.svn.wordpress.org/cleantalk-spam-protect/trunk@793896 b8457f37-d9ea-0310-8a92-e5e31aec5664