Beautiful emails

The idea of this pull request is to create beautiful email on Vosae. No more text-only emails (only on fallback).

Now email are beautiful, responsive, retina. :love_letter: 

I rewrote all the content, so we need to review all the sentences, and their translations.

- [x] Check if links in email are correct
- [x] HTML
- [x] Content
- [x] Translations