#60 relationship fields on download, defaults to name field

PR for #60

Hi @JedWatson,

This PR is still incomplete for this can only display Relationship's `name` field, I want to have a feedback first before continuing further.

Could you suggest a good way to display another field if 'name' is not available on the model?
I'm also thinking of using another field property so that it would be configurable in the model.
For example, instead of `User.name`, I would want to use `User.email` instead.