Add order_by option to Query.changes/2

[wkirschbaum]

Solves #113

I struggled to set up more than one change record for the test, so need some help there.

[maltoe]

@wkirschbaum

Thank you!

Could you add a line to top of the CHANGELOG.md as well?

## Unreleased

### Added

* .... (@wkirschbaum)

[wkirschbaum]

@maltoe thanks for the feedback and help. I updated the commit with the suggested changes I believe. Feel free to edit the commit if there is something small not to your liking.