Modules

A. Config generator:
- has a (long) list of optional keyword arguments, all of which have sensible defaults. Outputs a config file.

B. Data generator
- eats a config file, returns a data vector with added systematics and noise according to the model

C. Fitter
- eats a data vector and config file, fits parameters; returns an updated config file with new parameter values and ranges (we should decide how to record uncertainties)

D. Tension metric
- eats two config files, two data vectors, returns two chi-squares and one of several tension metrics describing a distance between the experimental results

E. Decider
- eats the chi-squareds, config files, and tension metrics. Returns a pair of updated config files; where tension and goodness-of-fit metrics have determined whether and how models have been updated; see #4 .