Z-Expansion fit using some data-thief'd results.

1. Extract results from json files.
2. Individually fit each result to Z-Expansion.
3. Plot each fit as a function of Q2.
4. At each Q2 point take values from each of the fits, take average and standard dev.
5. Fit the average and std lines to Z-Expansion. Extract error from difference in std and avg coeffs.
6. Calculate covariance, print results.