Use a local negotiator for translations
Use waitress for dev, support --reload
Change "button" tag with "a" tag

... and move "button" style in common
Update translations

- french is the default language (in templates)
- update translations (FR and EN)
- add filter "safe" to accept markup in translations
Use "safe" filter on main title (on homepage).
Add mail address for "contact" page

... with translation (for default subject).
Add urls for the main blocks (on homepage).
Update translations with the last feddbacks.

... of Laurent Chemla
Update CSS file.
Fix: missing end tags.
Fix translation for "fork us" in french.
No bullshit, no stats at Google (ask by L. Chemla).
Use waitress instead of gunicorn for development.
Fix README.
Add meta tags for the website preview when sharing it.
Add static images (square logo).

Forgot them in the previous commit.
Use translations instead of conf variables

for the title and description.
Fix typo in comment.
Fix "mixed content blocked" warning in https.

The webfont was not loaded.
Fix style of the last feature block on mobile devices.