updating readme.txt

git-svn-id: https://plugins.svn.wordpress.org/responsive-gallery-lightbox/trunk@1003951 b8457f37-d9ea-0310-8a92-e5e31aec5664
updating...

git-svn-id: https://plugins.svn.wordpress.org/responsive-gallery-lightbox/trunk@1003953 b8457f37-d9ea-0310-8a92-e5e31aec5664