Move distributed install to userbenchmark (#1824)
Summary:
Add install script to userbenchmark directory. Each userbenchmark can install their own dependencies.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1824
Reviewed By: FindHao
Differential Revision: D48268234
Pulled By: xuzhao9
fbshipit-source-id: d566bfa782e1a31fed456d5bcb38f3074e0284f5
