Add numpy to requirements.txt

[D4D3VD4V3]

run.py imports numpy which is not specified in requirements.txt

[de-viant]

same with 'six', it tries to import but it isn't present in requirements.txt

[m1nhtu99-hoan9]

This repo is abandoned by the author, I guess.

However, as numpy is already a peer dependency implicitly required by torch, I think adding it to requirements.txt doesn't make a difference. But the case for six, I do think that it needs to be present in requirements.txt.