change readme file

git-svn-id: https://plugins.svn.wordpress.org/sh-slideshow/trunk@863903 b8457f37-d9ea-0310-8a92-e5e31aec5664
update shslideshow.php file

git-svn-id: https://plugins.svn.wordpress.org/sh-slideshow/trunk@863905 b8457f37-d9ea-0310-8a92-e5e31aec5664