autocompleteのC-n C-pで補完を選択できるようにする

gistfile1.el

(require 'auto-complete)↓                                                       
(require 'auto-complete-config)↓                                                
(global-auto-complete-mode t)↓                                                  
;;C-n と C-pで補完を選択できる↓                                                 
(add-hook 'auto-complete-mode-hook↓                                             
          (lambda ()↓                                                           
            (define-key ac-completing-map (kbd "C-n") 'ac-next)↓                
            (define-key ac-completing-map (kbd "C-p") 'ac-previous)))↓                                                                         ↓