User ordering

Run the task new_ui:save_users

app/models/user/user.rb

@@ -1,6 +1,8 @@
 class User
   
   include Mongoid::Document
+  include Mongoid::Tree
+  include Mongoid::Tree::Ordering # use mongoid-tree because mongoid-ordering needs mongoid(~>3.0)
   include Mongoid::Timestamps
 
   devise :database_authenticatable, :recoverable, :rememberable, :trackable, :registerable, :validatable #, :timeoutable