New tutorial: Network analysis for infectious disease spread

[rossbar]

Last week I stumbled upon this paper, which ultimately led me down a rabbit hole w.r.t. the basic modeling of infectious disease with networks.

Given the accessibility of the data, it also struck me as a great candidate to try to reproduce some of the results in the paper. There's a lot more that could be done here (e.g. incorporating the temporal information to estimate the changes in R_0 of the course of the outbreak), but I wanted to keep the scope as narrow as possible to start.

Caveat: I am by no means an epidemiologist! The example is very simple, but some domain knowledge to validate/challenge some of the choices I made would be important. In particular, the choice to model the transmission network as a digraph (using the degree for the R_0 calculation) and relying on mean and var as estimates of the moments of the degree distribution deserve thorough attention.

[dschult]

Nice -- Well written; topic is relevant and interesting; provides an avenue to explore both graphically and numerically/statistically; and shows some of the complexity and difficulty in approaching the question of estimating R_0.

I approve this PR. I left a comment below, mostly to have you look at that sentence again.