Add Segment.IO key to .env.production template

:fork_and_knife: 

This PR adds an entry to the `.env.production` template, and pulls that resource out of the deploy resource in order to test its contents, and to trigger Unicorn/Sidekiq restarts when its contents change.

We tried to extract this template resource before, but didn't preface it with the `shared` directory resource, and so new nodes failed to converge and the extraction was quickly reverted. This PR makes sure to define the `shared` directory before defining the `.env.production` template. Nodes new and old converge and verify just fine.