install pytorch-cuda & tensorflow-gpu

[casperdcl]

Because they're very fiddly, I've now included pytorch-cuda and tensorflow-gpu in the CI by default.

Also updated the readme with instructions for how to reproduce locally.

Tested working with:

import tensorflow, torch
print(tensorflow.config.list_physical_devices("GPU"))
print(torch.cuda.is_available())

/CC @gschramm @alexdenker

[KrisThielemans]

Fine for me. Who asked for monai, by the way?

[gschramm]

I also experience that tensorflow / pytorch cuda installation from pypi can be tricky (very sensitive to the local cuda version). However, installing them from conda-forge is usually quite stable since they will ship the correct cuda version.

[casperdcl]

conda refused to install both for me in the image, unfortunately.

Meanwhile monai is purely for tensorboard3D, which is frustratingly not working KitwareMedical/tensorboard-plugin-3d#69