update readme.txt

git-svn-id: https://plugins.svn.wordpress.org/css3lightbox/trunk@950205 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update readme.txt

git-svn-id: https://plugins.svn.wordpress.org/css3lightbox/trunk@950207 b8457f37-d9ea-0310-8a92-e5e31aec5664
update readme.txt

git-svn-id: https://plugins.svn.wordpress.org/css3lightbox/trunk@950209 b8457f37-d9ea-0310-8a92-e5e31aec5664