title: Collapse items of Angular-NestedSortable / angular-ui-tree
body: <p>we're trying Angular-NestedSortable <a href="https://github.com/subvertnormality/Angular-NestedSortable" rel="nofollow">https://github.com/subvertnormality/Angular-NestedSortable</a> (the version 2 of angular-ui-tree doesn't look stable yet, looking at the tests).<br>
  We'd like to load the tree structure via REST and then collapse the root nodes.<br>
  Also, we'd like to make additional REST requests when an item is expanded.
  We have problems because the NestedSortable uses lots of nested Angular scopes and we don't understand how to access API methods like collapseAll() or how to overload toggle().<br>
  Can someone provide an example fiddle or plunkr or so?<br>
  That doesn't work:
  <code>$scope.list = [...]; $scope.collapseAll();</code>
  because <code>collapseAll</code> is not defined in the outer scope...</p>