Support to child routes

I'm using child routes with success in apigility, but the zfcampus/zf-apigility-documentation package apparently don't support the child routes.

Notice: Undefined index: my.route/is-child in [./vendor/zfcampus/zf-apigility-documentation/src/ApiFactory.php on line 190](https://github.com/zfcampus/zf-apigility-documentation/blob/1.1.0/src/ApiFactory.php#L190)

Someone have any solution ?
