change responsive.js

( function( window, $, undefined ) {
	'use strict';

	$( 'nav' ).before( '<button class="c-hamburger c-hamburger--htx" role="button" aria-pressed="false"><span>toggle menu</span></button>' ); // Add toggles to menus
	$( 'nav .sub-menu' ).before( '<button class="sub-menu-toggle" role="button" aria-pressed="false"></button>' ); // Add toggles to sub menus

	// Show/hide the navigation
	$( '.c-hamburger, .sub-menu-toggle' ).on( 'click', function() {
		var $this = $( this );
		$this.attr( 'aria-pressed', function( index, value ) {
			return 'false' === value ? 'true' : 'false';
		});

		$this.toggleClass( 'is-active' );
		$this.next( 'nav, .sub-menu' ).slideToggle( 'fast' );

	});

})( this, jQuery );