Use Hermes for both SMS and email

I've removed the mailgun-settings for the store-model, and replaced it with hermes_session (Hermes requieres a god key on a realm to send messages through it).

Everything regarding messaging the user (mobile & email) is now outsourced to Hermes, making the Vanilla code cleaner.

I've updated the specs, and they pass allright. However, this branch probably should be tested in a real life environment before it's put in production.