title: Wordpress add a class to menu link
body: <p>I need your help. I need to add a specific class on the link that wordpress generates in the menu.
  What should I edit?
  The HTML output in my case is:</p>
  
  <pre><code>&lt;nav class="nav" role="navigation"&gt;
  &lt;ul&gt;
  &lt;li id="menu-item-8" class="menu-item menu-item-type-post_type menu-item-object-page menu-item-8"&gt;&lt;a href="example.com"&gt;Sample Page&lt;/a&gt;&lt;/li&gt;
  &lt;li id="menu-item-9" class="menu-item menu-item-type-custom menu-item-object-custom menu-item-9"&gt;&lt;a href="http://example.com"&gt;Prova sample&lt;/a&gt;&lt;/li&gt;
  &lt;/ul&gt;&lt;/nav
  </code></pre>
  
  <p>the code in the header file that generate the menu is:</p>
  
  <pre><code>    &lt;!-- nav --&gt;
      &lt;nav class="nav" role="navigation"&gt;
      &lt;?php html5blank_nav(); ?&gt;
      &lt;/nav&gt;
     &lt;!-- /nav --&gt;
  </code></pre>