Add pytorch demo script

[wanzysky]

500 iters:

1500 iters:

[oiao]

Thanks a lot for the implementation. I have noticed a strange behavior of Pytorch:
When concatenating the return value of LinearNormalGamma at

evidential-deep-learning/torch_hello_world.py

Line 22 in 71ebd59

return mu, self.evidence(logv), self.evidence(logalpha) + 1, self.evidence(logbeta)

such that:

ret = mu, self.evidence(logv), self.evidence(logalpha) + 1, self.evidence(logbeta)
return torch.cat(ret, dim=-1)

the training does not seem to progress and a constant value is predicted. Is there any reasonable explanation for this?