Webfont headline medium in articles

- Remove semibold headline font
- Use headline serif in articles on tablet (see screenshot)

![screen shot 2013-07-11 at 17 14 34](https://f.cloud.github.com/assets/85783/782975/02b4e54a-ea45-11e2-9d02-e4a550c5b4db.PNG)

![Boom](http://i.imgur.com/UA3XKTA.gif)