Update readme.txt

git-svn-id: https://plugins.svn.wordpress.org/adsense-click-fraud-monitoring/trunk@758994 b8457f37-d9ea-0310-8a92-e5e31aec5664
compatible up to wp 3.6

git-svn-id: https://plugins.svn.wordpress.org/adsense-click-fraud-monitoring/trunk@758996 b8457f37-d9ea-0310-8a92-e5e31aec5664