Add minor_update and change_description fields to edit form

This depends on uncommitted changes to content_models that will follow later.
Add Timecop
Add integration tests for new publish behaviour

This is actually implemented in the models in govuk_content_models.
Update to new gemfury source URL format

See http://blog.gemfury.com/post/43472005936/unleash-the-fury-io
Indentation
Merge pull request #20 from alphagov/change_metadata

Add travel advice fields to track change metadata