$(function() {
  $('#sortable-tree .sortable').nestedSortable({
    handle: 'div',
    items: 'li',
    toleranceElement: '> div',
    placeholder: 'placeholder',
    maxLevels: 5,
    opacity: 0.6,
    forcePlaceholderSize: true,
    update: function() {
      var serialized = $(this).nestedSortable('serialize');
      $.post($(this).data('url'), serialized, function(data) {});
    }
  });
});