Update outside_controller_use.md (#2047)
Update outside_controller_use.md (#2047)

* Update outside_controller_use.md

Provide example for options parameter when serializing a resource.
ScottKbka/active_model_serializers,cassidycodes/active_model_serializers,ScottKbka/active_model_serializers,ScottKbka/active_model_serializers,nurey/active_model_serializers,rails-api/active_model_serializers,fabianoleittes/active_model_serializers,nurey/active_model_serializers,nurey/active_model_serializers