* sortable: transfer option "dropOnMouseleave" to droppable.

src/js/sortable.js

@@ -74,6 +74,7 @@
             nested      : !!containerSelector,
             mouseButton : options.mouseButton,
             noShadow    : options.noShadow,
+            dropOnMouseleave    : options.dropOnMouseleave,
             stopPropagation : options.stopPropagation,
             start: function(e) {
                 if(dragCssClass) e.element.addClass(dragCssClass);