Update README & `requirements.txt` to accurately reflect dependency versions

[e13h]

This comment from #17 leads me to believe that seamseg is now compatible with PyTorch >1.1. Could we please update the README and the requirements.txt files to reflect this?

With the latest changes from today, Seamseg should now be compatible with PyTorch 1.5.0. Can you please confirm?

Originally posted by @ducksoup in #17 (comment)