add Changelog text

git-svn-id: https://plugins.svn.wordpress.org/slider-image/trunk@975338 b8457f37-d9ea-0310-8a92-e5e31aec5664
edit changelog text

git-svn-id: https://plugins.svn.wordpress.org/slider-image/trunk@975339 b8457f37-d9ea-0310-8a92-e5e31aec5664