title: Display a custom field under WooCommerce single product title
body: <p>I have problem with a custom fields in WooCommerce. </p>
  
  <p>I have tille of product (book) and i want add author with custom field. I done it with register in theme custom fields and i add new one with Wordpress custome field. </p>
  
  <p>Custom fields call: <strong><code>product_author</code></strong> (that is my)  and <strong><code>mbt_publisher_name</code></strong> (from theme)</p>
  
  <p>I have found the template file <strong><code>title.php</code></strong> in theme and in woocommerce directory. </p>
  
  <p>I tried to add:</p>
  
  <pre><code>&lt;?php echo get_post_meta($id, "product_author", true); ?&gt; 
  </code></pre>
  
  <p>and nothing change... 
  orignal source from title.php </p>
  
  <pre><code>    &lt;?php
  /**
   * Single Product title
   *
   * @author  WooThemes
   * @package WooCommerce/Templates
   * @version 1.6.4
   */
  
  if ( ! defined( 'ABSPATH' ) ) {
      exit; // Exit if accessed directly
  }
  
  ?&gt;
  
  &lt;h2 itemprop="name" class="product_title entry-title"&gt;&lt;?php the_title(); ?&gt;&lt;/h2&gt;
  </code></pre>
  
  <p>what should I do to display that custom field under title? <br>
  Where I can find that hook? </p>
  
  <p>Thanks</p>