README: Several fixups.
README: Several fixups.

* Upgrade: proper header hierarchy, more sensible place in README.
* Translations: added Russian.

viaregio/django-newsletter,viaregio/django-newsletter,ctxis/django-newsletter,ctxis/django-newsletter,dsanders11/django-newsletter,dsanders11/django-newsletter,dsanders11/django-newsletter,ctxis/django-newsletter