fix cooprate with yasnippet

auto-complete-config.el

(defun ac-yasnippet-candidates ()
  (with-no-warnings
    (if (>= (string-to-number yas/version) 0.7)
        (apply 'append (mapcar 'ac-yasnippet-candidate-1 (yas/get-snippet-tables)))
      (if (fboundp 'yas/get-snippet-tables)
          ;; >0.6.0
          (apply 'append (mapcar 'ac-yasnippet-candidate-1 (yas/get-snippet-tables major-mode)))
        (let ((table
               (if (fboundp 'yas/snippet-table)
                   ;; <0.6.0
                   (yas/snippet-table major-mode)
                 ;; 0.6.0
                 (yas/current-snippet-table))))
          (if table
              (ac-yasnippet-candidate-1 table)))))))