Add a feature testing local government flag
Redo email signup features

Email signup feature text was a little bit insane due
to the need to stub/expect calls to govuk_delivery_client
before any actions were taken.

This reworks the tests to use a retrospective stub instead,
allowing test cucumber to be written in a sane way.
Remove refutive steps from email signup features

in response to David H's feedback.
Remove redundant setup steps

after removing the negative tests from the previous scenarios these
setup steps are no longer needed.
Merge pull request #1247 from alphagov/notifications-for-people-and-roles-fixes

Notifications for people and roles - add a feature covering the relevant_to_local_government flag.