/**
  * @name updateMetadata
  *
  * Extends $owner Metdata() function with Authorship values.
  *
  * @param string $metadata
  * @param SiteTree $owner
  * @param SiteConfig $config
  * @return string
  */
 public function updateMetadata(&$metadata, $owner, $config)
 {
     // variables
     // 		$config = SiteConfig::current_site_config();
     // 		$owner = $this->owner;
     $authors = $owner->Authors();
     $metadata .= $owner->MarkupHeader('Google+ Authorship');
     // Facebook Authors
     foreach ($authors as $author) {
         if ($author->FacebookProfileID) {
             $metadata .= $owner->MarkupFacebook('article:author', $author->FacebookProfileID, false);
             break;
         }
     }
     // Google+ Authors
     foreach ($authors as $author) {
         if ($author->GoogleProfileID) {
             $profile = 'https://plus.google.com/' . $author->GoogleProfileID . '/';
             $metadata .= $owner->MarkupRel('author', $profile);
             // @todo kinda - Google+ does not support multiple authors - break loop
             break;
         }
     }
     // Google+ Publisher
     if ($config->GoogleProfileID) {
         $profile = 'https://plus.google.com/' . $config->GoogleProfileID . '/';
         $metadata .= $owner->MarkupRel('publisher', $profile);
     }
     // return
     return $metadata;
 }