`type` as a function

[jamesplease]

Many enterprisey APIs don't respect the Accept header, so even if you specify JSON you may get something else entirely back. i.e.; old Java/Apache web servers frequently return text stack traces for any error.

It's convenient to be able to dynamically specify the type based on this.

i.e.;

// this API returns stack trace errors ;.;
type(response) {
  return response.ok ? 'json' : 'text';
}

Related: #24

---

(I know I've been opening a million issues. I plan to resolve them! Lots to do...I'll get to it ✌️ )