Include tree/trait data in the package for examples

[ScottClaessens]

Probably something from evolutionary biology - famous datasets?

[ScottClaessens]

I've added the following datasets in 02fc99a:

• Data on political and religious authority in Austronesian societies (see paper)
• Data on brain size, body size, diet, and sociality in primates (see paper)

It would be good to update examples to use these datasets instead of simulated data.

[ScottClaessens]

Updated documentation in 8d9c1a5. Closing this now.