title: Fields "created" and "modified" are not set automatically in CakePHP3.0.0(dev preview 2)
body: <p>I started to use CakePHP3.0 by mere curiosity. 
  To familiarize myself with the new features of CakePHP3.0, I followed the blog tutorial in official website(<a href="http://book.cakephp.org/3.0/en/tutorials-and-examples/blog/blog.html">http://book.cakephp.org/3.0/en/tutorials-and-examples/blog/blog.html</a>). What I did was just simply copy and past of the source code there. 
  Everything works fine, EXCEPT FOR fields "created" and "modified" not being saved. They just stay NULL. I have confirmed that this feature works fine in CakePHP 2.4.6. Below is the table definition and function add() for the blog tutorial.</p>
  
  <pre><code>CREATE TABLE articles (
      id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
      title VARCHAR(50),
      body TEXT,
      created DATETIME DEFAULT NULL,
      modified DATETIME DEFAULT NULL
  );
  
  public function add(){
      $article = $this-&gt;Articles-&gt;newEntity($this-&gt;request-&gt;data);
      if($this-&gt;request-&gt;is("post")){
          if($this-&gt;Articles-&gt;save($article)){
              $this-&gt;Session-&gt;setFlash("Success!");
              return $this-&gt;redirect(["action"=&gt;"index"]);
          }
          $this-&gt;Session-&gt;setFlash("Fail!");
      }
      $this-&gt;set(compact("article"));
  }
  </code></pre>