Remove the footer images
High DPI for all the things!

* Replace Glyphicons with with Font Awesome.
* Add high DPI support to comment avatars.
* Add high DPI sprite.
* Add high DPI support to the Tetris canvas.
* Move sprite css into a namespace.
* Fix apple-touch-icon paths.
Use the `.no-*` Modernizr classes
Use the TelegramaRender font in Tetris