Changed ratio display value to percentage

git-svn-id: https://plugins.svn.wordpress.org/compress-png-for-wp/trunk@1043079 b8457f37-d9ea-0310-8a92-e5e31aec5664
Changed ratio display value to percentage

git-svn-id: https://plugins.svn.wordpress.org/compress-png-for-wp/trunk@1043080 b8457f37-d9ea-0310-8a92-e5e31aec5664