I want to add env variables to new instances

I want all my deployments to have access to postgres, thus I'm creating a plugin which sets up a new user with access to a new database (on a postgres server in a different container). I want to expose the database access with an env variable, just like heroku does. To me it looks like release is the best place to put this hook.
Merge pull request #134 from phaza/patch-1

I want to add env variables to new instances