incorrect links in demo

[IVarha]

Subject of the issue

When I am trying to use your demo, I've get problem with downloading a data, namely incorrect links.

python demos/unpaired_mr_brain/demo_data.py

Exception: URL fetch failure on https://github.com/acasamitjana/Data/raw/master/L2R_Task4_HippocampusMRI.tar: 404 -- Not Found

[YipengHu]

@acasamitjana if you send me a copy of these test data, i can fix this link.