Added a new file for SNR calculations.
Added functions from notebook.
Various fixes to these functions
Edited functions to incorporate comments
Various fixes
TST: Subtle bug in optimized canonical model *on some platforms*.

This deals with situations in which the optimization sometimes proposes nan's
as solutions to the optimization problem.
Various fixes to incorporate comments
Initial tests for snr module
Changed model fit from using looping to using matrix operations. Changed fit from polyfit to least squares.
Fix to slope function and added a test for it.
Fixed last line.
Files mysteriously disappeared.  Readding them.
Some fixes to snr.py.  Progress on making model_fit.py more modular.
Completed modular transformation and added doc strings.
Some fixes to doc string.
Removed some commented lines.
Changed test of model_fit.py to reflect new modular form.
Fixed inputs to log_prop_vals of model_fit.py.
Relicensing for open-sourcing.
Merge pull request #5 from klchan13/model_fit

Model fit
Working towards final versions of paper figure notebooks.