Change meta font to Text Sans

Note that there are no changes on mobile, since we load Text Sans starting at desktop breakpoint only.

![screen shot 2014-08-18 at 17 00 21](https://cloud.githubusercontent.com/assets/85783/3954664/b47559b8-26f8-11e4-8712-d6d12e92aed0.PNG)
![screen shot 2014-08-18 at 17 00 11](https://cloud.githubusercontent.com/assets/85783/3954666/b480abb0-26f8-11e4-8ce4-23565ef68512.PNG)
![screen shot 2014-08-18 at 16 58 37](https://cloud.githubusercontent.com/assets/85783/3954665/b47fef7c-26f8-11e4-8096-3f6d493e23fb.PNG)
![screen shot 2014-08-18 at 18 12 18](https://cloud.githubusercontent.com/assets/85783/3954809/da00271a-26fa-11e4-8fad-910421be3dde.PNG)


![ ](http://media.giphy.com/media/mnEPOhKIE9iJq/giphy.gif)
When Opera Mini is better we can remove the px fallback in head files. Should take a few months for the update to be rolled out, though.