Fixed call to queryset object for Django >= 1.7

adminsortable/admin.py

@@ -44,7 +44,9 @@ class SortableAdminBase(object):
         object_tools block to take people to the view to change the sorting.
         """
 
-        if get_is_sortable(self.queryset(request)):
+        qs_method = getattr(self, 'get_queryset', self.queryset)
+
+        if get_is_sortable(qs_method(request)):
             self.change_list_template = \
                 self.sortable_change_list_with_sort_link_template
             self.is_sortable = True