Allow returning responses as json.

[mindreader]

In order to persist stripe information to our database for faster retrieval, I found I had written a wrapper that was decoding stripe schemas manually into json, then storing it in json, then trying to fetch the json back out into structs. When the api version changes this gets complicated due to incompatibilities (like Stripe.Discount used to exist, now it doesn't, or just in general new fields that exist or are removed).

I really could just be storing the json from stripe and then converting these back into stripe structs for my code to make use of, getting stripity stripe out of the chain.