`simulate_experiment_responses` should work with design?

[nhpackard]

Only way I could get it to work was to first call random_experiments_with_responses to generate experiments, then hand over those experiments to simulate_experiment_responses.

Maybe simulate_experiment_responses should have identical args to random_experiments_with_responses?

Maybe names should also be parallel, e.g.
random_experiments_with_responses
simulated_experiments_with_responses