update readme.txt, change little details to be the same as WP 3.9

git-svn-id: https://plugins.svn.wordpress.org/jm-html5-and-responsive-gallery/trunk@895826 b8457f37-d9ea-0310-8a92-e5e31aec5664
update readme.txt

git-svn-id: https://plugins.svn.wordpress.org/jm-html5-and-responsive-gallery/trunk@895828 b8457f37-d9ea-0310-8a92-e5e31aec5664