Responsive April campaign + assets on mozfr server, and other fixes

Responsive design was broken on mobile because of the April campaign, this PR gives some love to small screens :)
Also fixes:
- CSP issues for downloaded fonts on mozfr.org (www.mozfr.org was okay)
- Unix line ending on a couple of files
- Links on Tabzilla for Firefox/TB
- Typo on the sidebar (lettre d'information)

Can be tested here http://mozfr.theochevalier.fr/