Add `scipy.optimize.Result` to API docs

The return value of `scipy.optimize.minimize` is a `scipy.optimize.Result` object as described here:
http://docs.scipy.org/doc/scipy-dev/reference/generated/scipy.optimize.minimize.html

But `scipy.optimize.Result` is currently missing from the scipy API docs.
I guess all that is needed is to list it in the docstring here?
https://github.com/scipy/scipy/blob/master/scipy/optimize/__init__.py
But I wasn't sure where to put it ... a new section at the end?