Fixed bug in ArticleController.php example.

I believe that there is a bug in this code example. I'm unsure about this as I'm new to CakePHP.
I would receive a syntax error when going to `http://localhost/cakephp/articles`:

    Error: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'findAll' at line 1

I used the blog tutorial, using `PostsController.php` as an example.