Turn on kerning and ligatures

Aware of [this](https://github.com/guardian/frontend/pull/5216), but couldn't reproduce so possibly fixed in latest versions

### Before

![screen shot 2014-11-27 at 17 06 56](https://cloud.githubusercontent.com/assets/74132/5220108/2e73b9ea-7658-11e4-83ad-85ee950dd0eb.png)

### After

![screen shot 2014-11-27 at 17 06 45](https://cloud.githubusercontent.com/assets/74132/5220110/31c1cc54-7658-11e4-8e7f-03f59a5f65c0.png)