public function update()
    {
        $update_url = 'https://raw.github.com/ai/autoprefixer-rails/master/vendor/autoprefixer.js';
        $local_path = __DIR__ . '/vendor/autoprefixer.js';
        $new = file_get_contents($update_url);
        $old = file_get_contents($local_path);
        
        if (md5($new) == md5($old)) return false;
        
        file_put_contents($local_path, $new);
        return true;
    }