### Links to any relevant github issues:

- [Issue description](http://example.com/org/repo/issues/411). Any other useful information.

### What's in the the PR

- [ ] A description of the changes proposed in the pull request.
  - [ ] Any areas or issues reviewer should pay attention to? (comments in diff okay).
- [ ] Update `/docs` to include, whenever possible, a new, suitable recommendation about how to use
    the feature.
- [ ] Extra Credit: [Confirm it runs and tests pass on the Rubies specified in the Travis
  config](.travis.yml). A maintainer will otherwise confirm it runs on these.
- [ ] *Bonus Points* Update [CHANGELOG.md](https://github.com/rails-api/active_model_serializers/blob/master/CHANGELOG.md)
  with a brief description of any breaking changes, fixes, features, or
  miscellaneous changes at the top of the proper version section.

For more general information, see [Submitting a pull request](
https://github.com/rails-api/active_model_serializers/blob/master/CONTRIBUTING.md#submitting-a-pull-request-pr).