add appropriate install_requires (#23722)
Summary:
This adds:
- dependency on numpy if compiled with numpy support
- dependency on future if python <= 2.7
Fixes https://github.com/pytorch/pytorch/issues/23670
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23722
Differential Revision: D16643824
Pulled By: soumith
fbshipit-source-id: 5cf4d79cd188678cb2328c4286eabd52a2a86fcd
