Many pylint fixes to varstrut.py
Switched scipy optimize functions
Added simulation-based tests of nested and AR covariance structures
added multinomial logit; eliminated cycles; other refactoring and cleanup
remove renamed file
Refactored simulation check scripts
Added Mancel DeRouen robust sandwich estimate of standard errors
Added marginal effect estimates to GEE; seems to work but minimal test coverage
Set simulation tests to run under main
Forgot to push this file
Improved reporting of convergence troubles
Refactor ordinal/nominal setup code for ease of use
Refactor ordinal/nominal setup code for ease of use
Add missing test dataset
Fixed error in naive covariance calculation.
reuse cholesky factors in fit
Use smaller test data sets
Use smaller test data sets
Add covariance type to summary
Rename varstruct to covstruct, fix all errors in test_gee.py