Use "read-kbd-macro" insted of "kbd"

### 問題

kbd の docstring には "KEYS should be a string constant" とあります。

```
(defmacro kbd (keys)
  "Convert KEYS to the internal Emacs key representation.
KEYS should be a string constant in the format used for
saving keyboard macros (see `edmacro-mode')."
  (read-kbd-macro keys))
```

### 解決案

kbd ではなく read-kbd-macro を使うと、このエラーが発生しません。

```
(read-kbd-macro coffee-find-other-file-key)
;; => "f"
```

### 検証環境

(emacs-version)
;;=> "GNU Emacs 24.2.1 (x86_64-pc-linux-gnu, GTK+ Version 3.6.4)  of 2013-04-09 on allspice, modified by Debian"