misc. fix with CSS overlay

git-svn-id: https://plugins.svn.wordpress.org/microstock-photo-plugin/trunk@894960 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated readme file

git-svn-id: https://plugins.svn.wordpress.org/microstock-photo-plugin/trunk@894969 b8457f37-d9ea-0310-8a92-e5e31aec5664