probable faulty data augmentation - numpy seed initialization

[e-maud]

The random seed initialisation using numpy might be faulty:

https://www.reddit.com/r/MachineLearning/comments/mocpgj/p_using_pytorch_numpy_a_bug_that_plagues/

Many thanks for checking and, ideally, correcting. Happy to help if needed.

[RPetitpierre]

Corrective pull request #5