Implementing graph convolutional neural networks

[hector-crean]

Given the recent popularity of graph convolutional neural networks (i.e. https://github.com/tkipf/gcn), would it be worth implementing a swift paradigmatic version? I have a semi-working version, but would defer to those more knowledgable in these things.

[BradLarson]

That would be a great addition. It's something that I know a few people were exploring, but we don't have any formal examples in the repository yet.

The integration of graphs and tensor operations is somewhere that we believe Swift can really shine, so anything you'd be willing to contribute would be very much appreciated.