Documentation from 7D7D

[tbenthompson]

Model interface:

• sim_batch
• family
• family_params

Grid interface:

• get_theta, get_null_truth and so on

Null hypothesis interface:

• ip.hypo

Why do we pass the class rather than a constructed object?

Change K to n_sims for clarity. Except perhaps in a calibration-specific context where it's nice to match with paper formulas.