Add published_at date to visible metadata for DSU documents
Rename "Registrations" to "Registration"

[Trello
ticket](https://trello.com/c/e3yKYxH3/377-change-registrations-to-regist
ration-on-finder-frontend-for-aaib-reports)

I have also added an integration test for AAIB Reports, as that was
missing.
Merge pull request #56 from alphagov/rename-registrations-to-registration

Rename "Registrations" to "Registration"
Rename `published_date` => `published_at`
Merge pull request #55 from alphagov/feature/add-published-at-to-dsu

Add published_at date to visible metadata for DSU documents
Add MAIB report format

This commit adds a presenter for the MAIB Report and calls that
correctly from the specialist documents controller.

It also adds a feature for testing viewing of MAIB Reports.
Merge pull request #57 from alphagov/maib-reports

Add MAIB report format
Fix typo in MAIB feature
Add RAIB report format

This commit adds the ability for Specialist Frontend to render RAIB
reports. This contains a presenter which is called from
specialist_documents_controller and a features for testing viewing
RAIB reports.
Merge pull request #59 from alphagov/fix-typo-in-feature

Fix typo in MAIB feature
Merge pull request #58 from alphagov/raib-reports

Add RAIB report format
Singularise MAIB and RAIB report types

A report can't be a safety bulletins.
Merge pull request #60 from alphagov/singular-maib-and-raib-report-types

Singularise MAIB and RAIB report types