title: Selecting an node by attribute with Goutte / Symfony CssSelector component
body: <p>I'm using <a href="https://github.com/fabpot/Goutte" rel="nofollow">Goutte</a> (which is a standalone package of the Symfony functional testing components) to test a Wordpress theme:</p>
  
  <pre><code>public function testDocumentHasBasicNodes(){
      $this-&gt;assertEquals(1, $this-&gt;crawler-&gt;filter('title')-&gt;count(),
              'document shall have a TITLE node');
  
      $this-&gt;assertEquals(1, $this-&gt;crawler-&gt;filter('meta')-&gt;count(),
              'document shall have a meta[charset="utf-8"] node');
  }
  </code></pre>
  
  <p>The first test passes but:</p>
  
  <pre><code>indexTest::testDocumentHasBasicNodes
  document shall have a meta[charset="utf-8"] node
  Failed asserting that 0 matches expected 1.
  </code></pre>
  
  <p><strong>So to sum up my question:</strong><br>
  How do I get a node by attribute with Goutte / Symfony CSS Selector component?</p>