square/retrofit — pull request #588 by nerdwaller (2014-08-14 19:26:59+00:00)
Title: Parameterized Response Type (RestResponse<>)

This is something that I think many people want, and I needed for a project I am working on. It maintains backwards compatibility. I'd suspect in R2.0 it would be worth stripping this if you plan to make Response parameterized (as I read in the Docs pages).

You can see very basic usage support in the tests.