fix graphy.py interface to networkx

[Jpickard1]

• graph.py needs to be largely removed/refactored
• networkx should be a standard import used in HAT

[colltoaction]

Hi again :). Maybe the Levi graph will be of interest to you. It can represent hypergraphs as bipartite graphs. I wish to develop this idea myself as well. Something like HIF->NX Levi graph->Hypergraph (any library).

• https://en.m.wikipedia.org/wiki/Levi_graph
• https://ncatlab.org/nlab/show/hypergraph#hypergraphs_as_2colored_graphs

Long term I wish to see a library implemented 100% in terms of lower-order graph structures. Maybe NetworkX itself will catch up!