Add Recoder open source recommendation system package

[amoussawi]

Recoder is a Python package built with PyTorch for large-scale training of factorizaion models for collaborative filtering. For instance, you can get state-of-the-art results with an Autoencoder model fully trained on MovieLens-20M with implicit feedback in less than a minute

[grahamjenson]

I am closing this because it looks like the development on Recoder has stopped. If it picks up again, or has any more development please reopen and fix merge conflict and will happily merge :)