Merge pull request #665 from MITx/bug/kfiedler/sequnce-over-video

Added fix so that sequnce nave doesn't go over full screen videos

common/lib/xmodule/xmodule/css/sequence/display.scss

@@ -32,7 +32,7 @@ nav.sequence-nav {
 
   .sequence-list-wrapper {
     position: relative;
-    z-index: 9999;
+    z-index: 99;
     border: 1px solid #ccc;
     height: 44px;
     margin: 0 30px;