Remove unused classes and markup on consultations
Add share links to a few document formats

Specifically, consultations, news articles, speeches and
world location news articles.

https://www.pivotaltracker.com/s/projects/367813/stories/58710832
Send Analytics events for share links

https://www.pivotaltracker.com/s/projects/367813/stories/58710832
Merge pull request #1108 from alphagov/58710832-add-social-sharing-links

Add share links to a few document formats

https://www.pivotaltracker.com/s/projects/367813/stories/58710832
Update gds-sso gem

We need a newer version to get the organisation_slug back from signon
when doing user auth.

Basic auth support has been removed in the latest version.
User -> Organisation relationship keys by slug

Also includes a pending migration to drop organisation_id.
Remove ability to edit user organisation & email

Also tighten up the mass assignment protection for User and fix a few
tests that were using User.create and falling foul of the new changes.
Merge pull request #1099 from alphagov/get-user-organisation-from-signon

Get user organisation from signon

[Delivers https://www.pivotaltracker.com/story/show/60396766]