Log Message:
Update ruby-hashie to 3.5.6.

## [3.5.6] - 2017-07-12

[3.5.6]: https://github.com/intridea/hashie/compare/v3.5.5...v3.5.6

### Miscellaneous

* [#416](https://github.com/intridea/hashie/pull/416): Fix `warning: instance
  variable @disable_warnings not initialized` -
  [@axfcampos](https://github.com/axfcampos).