title: Wordpress Plugin template_redirect throws 404
body: <p>I'm trying to load a specific file of a plugin via a URL in Wordpress using template_redirect. The file gets shown correctly, however the header sent is 404, not 200.</p>
  
  <p>The code in the plugin is:</p>
  
  <pre><code>add_filter('query_vars','plugin_add_jb');
  function plugin_add_jb($vars) {
      $vars[] = 'jb_ajax';
      return $vars;
  }
  
  add_action('template_redirect', 'plugin_jb_check');
  function plugin_jb_check() {
      if(intval(get_query_var('jb_ajax')) == '1') {
          $jb_action = $_GET['action'];
          if($jb_action == 'refer') {
              include('./wp-content/plugins/JobBounties/ajax_refer.php');
          }
          elseif ($jb_action == 'refer_post') {
              include('./wp-content/plugins/JobBounties/ajax_refer_post.php');
          }
          exit;
      }
  }
  </code></pre>
  
  <p>Anyone have any idea why it's throwing 404?</p>