Article header & columning

First step of the desktop article designs, introducing:
- Right column (width: 4 cols)
- Left column (width: 3 cols)
- Comments appear below the article on wide viewports

Most of the layout changes do not follow our predefined breakpoints, as we use grid widths instead (for example, the right column appears when the viewport is 11 grid columns wide).

## Tablet (landscape)

![screen shot 2013-07-17 at 12 13 15](https://f.cloud.github.com/assets/85783/811373/726baaa4-eed2-11e2-950e-8c9b1572a82f.PNG)


## Desktop
![screen shot 2013-07-17 at 12 13 29](https://f.cloud.github.com/assets/85783/811370/63c31b9a-eed2-11e2-8d05-c282ae42ff9a.PNG)

![Bioman](http://i.imgur.com/vabBeMN.gif)