protected function createNavbarContainerClass(array $options)
    {
        // Create navbar container class
        $containerClass = 'navbar';
        if ($options['inverse']) {
            $containerClass .= ' navbar-inverse';
        }
        if ($options['fixed']) {
            $containerClass .= ' navbar-fixed-';
            switch ($options['fixed']) {
                case 'top':
                case 'bottom':
                    $containerClass .= $options['fixed'];
                    break;
                default:
                    throw new Exception\InvalidArgumentException(
                        'Only top and bottom are acceptable navbarFixed options'
                    );
            }
        }
        return $containerClass;
    }