Cleanup mailer spec

Improve subject of package confirmation email and extract it into I18n
Change confirmable behavior

Stop sending confirmation emails since there is no longer a way to sign
up for an account (for now).

* Remove `RecipientsController`
* Limit access to searching and creating users to desk workers
* Remove `User#skip_confirmation_email!`
* Remove custom `AccountsMailer` since custom devise emails are no
  longer needed.
Run specs in random order
Cleanup spec_helper and support modules

* Rename `EmailMacros` to `EmailSteps`
* Remove `FactoryGirlStepHelpers`
Cleanup chrome driver