leoliu/sokoban — pull request #1 by syohex (2013-03-28 08:48:18+00:00)
Title: Fix error for before Emacs 24.3

I got following error on Emacs 24.2 when I execute `M-x sokoban`.
Because 'read-only-mode' is introduced at Emacs 24.3.

```
save-current-buffer: Symbol's function definition is void: read-only-mode
```

Please see this patch.