Latex node labels in graph visualizations using NetworkX

[bhpayne]

NetworkX supports Latex for node labels on graphs; see https://networkx.org/documentation/networkx-1.9/examples/drawing/labels_and_colors.html

I think the problem was with long Latex strings, but I don't have an example showing that.

This is a subset of https://github.com/allofphysicsgraph/proofofconcept/issues/19

Using NetworkX for graph visualization would be in the same space as the current approaches, d3js and graphviz. See also #236