improvement for https://github.com/swayf/mongoose-path-tree/issues/6

Author: swayf

lib/tree.js

@@ -17,6 +17,7 @@ module.exports = exports = tree;
 function tree(schema, options) {
 
     var pathSeparator = options && options.pathSeparator || '#'
+        , wrapChildrenTree = options && options.wrapChildrenTree
         , onDelete = options && options.onDelete || 'DELETE' //'REPARENT'
         , numWorkers = options && options.numWorkers || 5
         , idType = options && options.idType || Schema.ObjectId
@@ -360,7 +361,10 @@ function tree(schema, options) {
             options.sort = {};
         }
         options.sort.path = 1;
-        options.lean = true;
+
+        if (options.lean == null) {
+            options.lean = !wrapChildrenTree;
+        }
 
         return this.find(filters, fields, options, function (err, results) {