Added Russian translation

@Proplex @stqism, did you forget to remove the email subscription lines or it's intentional? 

As far as translation goes, there are many common lines between [Tox/Tox-Website](https://github.com/Tox/Tox-Website) and here, it would be weird if some new contributor translated menu options (and other common translations) differently than ones from Tox/Tox-Website. You probably want to make a single top-level translation file for each language with all those `lf_title`, `nv_home`, `nv_about`, `nv_features`, `nv_contribute`, `nv_wiki`, `slogan`, `dev_links`, `dev_blog`, `dev_docsetc`, etc, and just leave page-specific lines in downloads/ file.

Translation file misses lines about Gentoo, etc.

Also, why do we have separate repos for the whole website and just for the downloads page? Will you be making a new repo for every single page you add? : ) Just merge this in Tox-Website. Not to mention that the header part of Downloads page is noticeably different from one on the main page, as if Downloads page was really developed in a separate repo by different web designers/developers:

![1](https://cloud.githubusercontent.com/assets/1855294/3573314/d51b2844-0b70-11e4-8c78-f62d1374443f.png)

![2](https://cloud.githubusercontent.com/assets/1855294/3573316/d776952e-0b70-11e4-8224-b887257c2374.png)