Check class exists before loading

git-svn-id: https://plugins.svn.wordpress.org/ml-slider/trunk@892981 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update readme

git-svn-id: https://plugins.svn.wordpress.org/ml-slider/trunk@892982 b8457f37-d9ea-0310-8a92-e5e31aec5664
Add textarea setting type

git-svn-id: https://plugins.svn.wordpress.org/ml-slider/trunk@892983 b8457f37-d9ea-0310-8a92-e5e31aec5664