WIP: Feature/signup

TODO:
- [x] Put CSRF token to DOM so it is compilable with Flask-wtf-csrf
- [x] Setup mandrill credentials to production environment
- [x] Set default email sender
- [x] Set email copy
- [ ] Tests to email service
- [x] Correct domain to activation links

You should also define `is_active` method that returns whether user is active or not: https://flask-login.readthedocs.org/en/latest/#your-user-class