After Setup Theme

/*From UnderScore Theme*/
if ( ! function_exists( 'myrex_setup' ) ) :
/**
 * Sets up theme defaults and registers support for various WordPress features.
 *
 * Note that this function is hooked into the after_setup_theme hook, which
 * runs before the init hook. The init hook is too late for some features, such
 * as indicating support for post thumbnails.
 */
function myrex_setup() {

    /*
     * Make theme available for translation.
     * Translations can be filed in the /languages/ directory.
     * If you're building a theme based on myrex, use a find and replace
     * to change 'myrex' to the name of your theme in all the template files
     */
    load_theme_textdomain( 'myrex', get_template_directory() . '/languages' );

    // Add default posts and comments RSS feed links to head.
    add_theme_support( 'automatic-feed-links' );

    /*
     * Enable support for Post Thumbnails on posts and pages.
     *
     * @link http://codex.wordpress.org/Function_Reference/add_theme_support#Post_Thumbnails
     */
    //add_theme_support( 'post-thumbnails' );

    // This theme uses wp_nav_menu() in one location.
    register_nav_menus( array(
        'primary' => __( 'Primary Menu', 'myrex' ),
    ) );

    /*
     * Switch default core markup for search form, comment form, and comments
     * to output valid HTML5.
     */
    add_theme_support( 'html5', array(
        'search-form', 'comment-form', 'comment-list', 'gallery', 'caption',
    ) );

    /*
     * Enable support for Post Formats.
     * See http://codex.wordpress.org/Post_Formats
     */
    add_theme_support( 'post-formats', array(
        'aside'
    ) );

    // Setup the WordPress core custom background feature.
    // add_theme_support( 'custom-background', apply_filters( 'myrex_custom_background_args', array(
        // 'default-color' => 'ffffff',
        // 'default-image' => '',
    // ) ) );
}
endif; // myrex_setup
add_action( 'after_setup_theme', 'myrex_setup' );