Introduce timecop
Add published_at date to DSU on publish!

Trello ticket: https://trello.com/c/ZW0i6nya/362-add-first-published-date-to-the-dsu-finder-3-1

Add published_at date to drug safety updates on #publish! As this is part of the metadata for DSU we should store this in the DrugSafetyUpdate class not the SpecialistDocument class.
Make sure published dates are reset on withdrawal
Display published_at field correctly within specialist-publisher
Rename published_at to first_published_at

We already apply a 'published_at' to RenderedSpecialistDocuments. To avoid
confusion, rename the new field to `first_published_at`
Merge pull request #289 from alphagov/feature/add-published-at-to-dsu

Add published at to DrugSafetyUpdates
Silly wabbit. %m is month, %M is minute.
Singularise MAIB Report types

A report can't be a safety bulletins
Merge pull request #296 from alphagov/fix-doh-with-strftime

Silly wabbit. %m is month, %M is minute.
Merge pull request #297 from alphagov/singularise-maib-report-types

Singularise MAIB Report types
Don't validate using `SafeHtml` from govuk_content_models

Keeping this in triggers an error where an uninitialised constant --
`GOVSPEAK_FIELDS` -- can't be found. After some discussion with @alext
we decided to remove this functionality as we probably don't want to
allow embedding HTML in `Attachment` objects.

There's also a (cucumber) test to prevent injection attacks so we know
doing this is safe.

The error as it appears when this is kept in:

`uninitialized constant Attachment::GOVSPEAK_FIELDS (NameError)`
Add support for RAIB reports

This PR contains the work in specialist-publisher for editors from the
"Rail Accident Investigation Branch" to publish reports. It contains:

 - the schema of the possible values of the facets in the RAIB Report
   form
 - the models, services, observers, repo and views for RAIB reports
 - adding RAIB editors to permission checker
 - testing RAIB Report workflow