Updating readme: tested up to 4.0

git-svn-id: https://plugins.svn.wordpress.org/drop-shadow-boxes/trunk@981670 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updating version

git-svn-id: https://plugins.svn.wordpress.org/drop-shadow-boxes/trunk@981671 b8457f37-d9ea-0310-8a92-e5e31aec5664