fixed screenshot.png directory

git-svn-id: https://plugins.svn.wordpress.org/log-user-stats/trunk@806024 b8457f37-d9ea-0310-8a92-e5e31aec5664
added screenshot.png

git-svn-id: https://plugins.svn.wordpress.org/log-user-stats/trunk@806025 b8457f37-d9ea-0310-8a92-e5e31aec5664