validate `family_of_curves`

[githubpsyche]

Continuing from #5, but with the new policy of creating new issues for new issues instead of just dumping all commentary related to family_of_curves here. I'll reference this issue where relevant so that I can still go here to keep track of existing and finished problems.

[githubpsyche]

There are quite a few "options" for this one but the real ones (i.e the ones w/ substantial associated code) are compute_likelihood, count_particles, get_curve_xy_vals.

Where are they used?

• compute_likelihood is called 3 times in the main function.
• count_particles occurs in both analyze_outputs and common_to_all_curves (within auto_generate, used for data simulation).
• get_curve_xy_vals is used in common_to_all_curves's draw_bcm_curve option and in simulate_data. draw_bcm_curve doesn't seem to ever actually get used in the codebase, though.

So as long as I validate both simulate_data and importance_sampler, I'll get family_of_curves along the way.

[githubpsyche]

A bug indexing cluster_idx in compute_likelihood is handled in #34