Handling 201s properly from `client.response()` by looking for the `Location` header or a URI in the `response.responseText` & making a subsequent `GET` to it which then resolves the original XHR request, updating `data.del()` & `data.set()` to allow CORS requests to be resolved by the server (headers might not always be available)

Forgot a `break`

Added braces for explicit meaning