Remove torch requirements in requirements.txt (#653)
Summary:
This PR removes all `torch` and its domain packages from `requirements.txt`.
It also adds check in `install.py` to make sure they are installed before installing the benchmark.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/653
Reviewed By: alanwaketan
Differential Revision: D33144152
Pulled By: xuzhao9
fbshipit-source-id: 266f8f570811fa27d32801117ac1da3443a7d89e
