Change slide functionality

git-svn-id: https://plugins.svn.wordpress.org/ml-slider/trunk@1028704 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fix php warning

git-svn-id: https://plugins.svn.wordpress.org/ml-slider/trunk@1028706 b8457f37-d9ea-0310-8a92-e5e31aec5664