Fix change feed serve issues

This change is for https://www.pivotaltracker.com/story/show/61556230

Fixes several issues: 

* Filters changes by passed actual (as_of) date as we do with other Tariff entities
* Make sure we display change record entries for deleted entities (change on Model::Operation#record)

Depends on frontend change https://github.com/alphagov/trade-tariff-frontend/pull/100