documentation around relationships

I'm starting to use motion_data_wrapper in a project I'm working on, and while it was extremely easy to drop in and start persisting individual models (thank you for that), I'm as yet unclear on the best way to model relationships. I've got the XCode/CoreData entity creation part down, but am just starting to poke around with the proper way to organize the ruby code. I don't think it's going to be that hard, but thought it would be a nice addition to the documentation. I'm new to ruby-motion and have almost no CoreData experience. I'm sure other people are in the same boat as me and have even less iOS experience.

Note: I'd be happy to contribute a pull request, after I learn how to do it myself. I was just hoping that someone with more experience could beat me to it.