Add in stagecraft integrations
Add in a test to ensure querist has been called

- check that the correct endpoint has been called in the underlying querist module
Added stagecraft tests.

Updated logic in stagecraft integration.

Added warn logger.
Fixed linting error
Change ordering of log messaging in stagecraft integration

- previously this would be set to `undefined` because I'm a dork, and now it's in the right order
dataset => dataSet and messages => Messages
Send emails once we have them
Added a safeMode with a stub transport for emailing.

This allows us to do dry runs before we send emails for reals.
Bump nodemailer to the latest version
Refactored the stub callback to live in emailer
Merge pull request #19 from alphagov/feature/stagecraft-integration

Add in tested integrations for backdrop and stagecraft endpoints