Reply to address

The MR contains commits from !24 (merged), I'll rebase this on master once !24 (merged) is merged

The only commit to review is 1985592b

This MR adds the Reply-To header to all emails sent out. (more context https://gitlab.com/gitlab-org/gitter/webapp/issues/2268#note_266748 be populated with no-reply@gitter.im. (part of https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1589)

webapp companion MR: https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1589

Testing strategy

This testing strategy is end to end and it involves both env and webapp repositories.

1. env repository
   1. checkout reply-to-address branch
   2. npm i
   3. npm link so we can link this module in webapp
2. webapp
   1. checkout 2268-no-reply-notification branch (https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1589)
   2. cd modules/env this is critical, we need to link dependency of this module, not the root project
   3. npm link @gitterhq/env
   4. go back to the root dir of webapp
   5. add mandrill secrets to your env https://gitlab.com/gl-gitter/secrets/blob/develop/webapp/prod#L6-7
   6. run ./scripts/utils/send-unread-notification-email.js -u <username> -r <room uri> --dummy false
      • username and room uri need to exist in our local database
3. see that email inbox associated with username got a notification and when you try to reply to it, you are replying to no-reply@gitter.im