Can I define a default ORDER BY for a relationship?
Your example foreign key definition doesn't make much sense...why would the foreign key be called "child" when it points at a Parent? I'm just going to assume this is a meaningless example...

At any rate, you can always just do:

``` python
class Category(Model):
    parent = ForeignKeyField("self", related_name="children_backref")

    @property
    def children(self):
        return self.children_backref.order_by(Category.name)
```

I want something like this:

``` python
child = ForeignKeyField(Parent, related_name="children", default_order_by="birthday")
```
