Geonomics

Added docstrings to all public-facing classes.

Fixed the validations-test code to run using the new (tskit-based) data structures of Geonomics. Also fixed bug Anusha found in mod.plot_genotype(), as well as the typo she found in the docs, and some other minor tweaks I've made along the way.

Got rid of sparse pairwise distance matrix that I was using to be lazy and that was a dumb choice that overloaded memory for large pops.

Also trying to figure out how to get the package to stop including the old Yosemite rasters.

Had not realized that I had left the code such that the nearest neighbor was always being chosen as a mate. Now implemented two new parameters, which together allow user to: 1.) either always choose nearest neighbor or to randomly choose from among individuals within the mating radius; 2.) if randomly choosing within the mating radius, probabilities of choosing each individual can be either uniform or inverse-distance weighted.

Changed the format of the params file a bit, and had to change some code to match that. Also tweaked the pop-size plotting method and some other small things.

Changed default neutral mutation rate to 0; cleaned up params-file formatting a bit; tweaked Yosemite demo.