blog design

Attempt to enhance blog design https://github.com/mix-it/linkit/issues/66

See [test instance](http://mixittest.mixit.cloudbees.net/article/6/pourquoi-ce-site-)

Changes the font of the entire website for Oxygen. See [test instance](http://mixittest.mixit.cloudbees.net/)

What do you think? @clacote @mpetitdant