`commonMethod()` now returns in same form as `request()`

Hey Dave,

This is an update that will break existing usage of the discovery client, but I feel it is a valuable improvement.

The change allows access to the contents of `request`'s `res` value, which contains essential information like the HTTP statusCode. Developers familiar and comfortable with `request()` will be right at home.

I've already monkey-patched this into our codebase, as I needed access to the HTTP status code to determine what was going on with a request.