functions.php

<?php

require __DIR__ . '/application.php';

if ( ! class_exists( 'Timber' ) ) {
    add_action( 'admin_notices', function () {
        echo '<div class="error"><p>Timber not activated. Make sure you activate the plugin in <a href="' . esc_url( admin_url( 'plugins.php#timber' ) ) . '">' . esc_url( admin_url( 'plugins.php' ) ) . '</a></p></div>';
    } );

    add_filter( 'template_include', function ( $template ) {
        return get_stylesheet_directory() . '/static/no-timber.html';
    } );

    return;
}

Timber::$dirname = array( 'templates', 'views' );

class StarterSite extends TimberSite {

    function __construct() {
        add_theme_support( 'post-formats' );
        add_theme_support( 'post-thumbnails' );
        add_theme_support( 'menus' );
        add_theme_support( 'html5', array( 'comment-list', 'comment-form', 'search-form', 'gallery', 'caption' ) );
        add_filter( 'timber_context', array( $this, 'add_to_context' ) );
        add_filter( 'get_twig', array( $this, 'add_to_twig' ) );
        parent::__construct();
    }


    function add_to_context( $context ) {
        $context['menu'] = new TimberMenu();
        $context['site'] = $this;

        return $context;
    }

    function add_to_twig( $twig ) {
        /* this is where you can add your own functions to twig */
        $twig->addExtension( new Twig_Extension_StringLoader() );

        return $twig;
    }

}

new StarterSite();