/** JASON ADDED THIS - BEGIN */

function menu_shortcode($atts) {
    extract(shortcode_atts(array(
        'menu' => '',
        'container' => 'div',
        'container_class' => '',
        'menu_class' => 'menu',
        'theme_location' => ''
    ), $atts));

    return wp_nav_menu(array(
        'menu' => $menu,
        'container' => $container,
        'container_class' => $container_class,
        'menu_class' => $menu_class,
        'theme_location' => $theme_location,
        'echo' => false
    ));
}
add_shortcode('menu', 'menu_shortcode');

/** JASON ADDED THIS - END */