MC-CNN requires pytorch >= 0.4.1

It appears that the current implementation of MC-CNN requires PyTorch version 0.4.1 (or above, I guess). Anyway, this is easy to solve and I will update the requirements and conda recipe accordingly.

@ageorge @ssarfjoo, since you are contributing to the package, be sure to keep that in mind when adding code (i.e. update the requirements and conda recipe as well in your MR).

Thanks !