images screenshots changes

git-svn-id: https://plugins.svn.wordpress.org/wp-vertical-image-slider/trunk@821309 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme.txt changes

git-svn-id: https://plugins.svn.wordpress.org/wp-vertical-image-slider/trunk@821310 b8457f37-d9ea-0310-8a92-e5e31aec5664