title: add custom attribute to wordpress navigation
body: <p>in wordpress admin panel when i create a nav menu , i can set title and class for each <code>&lt;a&gt;</code> in html structure .
  in wordpress codex we can add setting for <code>&lt;ul&gt;</code>  like below :</p>
  
  <pre><code>&lt;?php
  
  $defaults = array(
      'theme_location'  =&gt; '',
      'menu'            =&gt; '',
      'container'       =&gt; 'div',
      'container_class' =&gt; '',
      'container_id'    =&gt; '',
      'menu_class'      =&gt; 'menu',
      'menu_id'         =&gt; '',
      'echo'            =&gt; true,
      'fallback_cb'     =&gt; 'wp_page_menu',
      'before'          =&gt; '',
      'after'           =&gt; '',
      'link_before'     =&gt; '',
      'link_after'      =&gt; '',
      'items_wrap'      =&gt; '&lt;ul id="%1$s" class="%2$s"&gt;%3$s&lt;/ul&gt;',
      'depth'           =&gt; 0,
      'walker'          =&gt; ''
  );
  
  wp_nav_menu( $defaults );
  
  ?&gt;
  </code></pre>
  
  <p>the problem is how i can add some attribute  like <code>data-hover</code> in my nav generator of wordpress ? any body can help how can add custom attribute to each <code>&lt;a&gt;</code> of nav menu .</p>