fill and and standardize docstrings

[jGaboardi]

Docstrings within region models are in several formats and there are quite a few missing argument explanations and example uses. See also @knaaptime's comments here, here, and here.

This is a running list of tasks. Update as needed.

• [ ] azp
• [ ] azp_util
• [x] base (#294)
• [ ] components
• [ ] csgraph_utils
• [ ] maxp
• [ ] objective_function
• [x] random_regions --> 857603a
• [ ] region_k_means
• [x] skater --> (#335)
• [ ] spenc + spenclib/ (eec3ab2, ...)
• [x] util --> d73e20d
• [x] ward --> d6a1949