Updated readme

git-svn-id: https://plugins.svn.wordpress.org/image-mapper/trunk@937018 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated readme

git-svn-id: https://plugins.svn.wordpress.org/image-mapper/trunk@937019 b8457f37-d9ea-0310-8a92-e5e31aec5664