Configuration Options for shape of Batch GraphQL Return JSON

Awesome project you got going here, thanks for keeping this going. I've been using the batch option to allow for batch-GraphQL requests from ApolloClient, but it doesn't seem like there is an easy way to specify what shape I want the data to return in? Correct me if I'm wrong.

For example, currently when sending batch-requests, I get back a JSON array with the data I am interested in nested under a "data" key which is itself nested in a "payload" key.

```
[
{"payload":
{"data":
{