Update flexslider to 2.2.2

git-svn-id: https://plugins.svn.wordpress.org/ml-slider/trunk@890621 b8457f37-d9ea-0310-8a92-e5e31aec5664
Don't use CSS to hide the slides. The slides are hidden using inline CSS on the list element

git-svn-id: https://plugins.svn.wordpress.org/ml-slider/trunk@890624 b8457f37-d9ea-0310-8a92-e5e31aec5664