Ability to sort sub-resources

[dpalma]

I'd like to use sequelize ordering on a sub-resource of one of my top-level resources. I think this could be done by enhance the options that "associations" recognizes, when specified as an object. Something like this:

var groupResource = finale.resource({
    model: db.models.Group,
    actions: ['read'],
    associations: {
        Members: {
            order: ['index']
        }  
    }
});