Adding headline container

Adding a new container for the days headlines.
Allows for standard and big size stories only.

Logic is:
* 2 standard stories per column
* 1 big story per column
* Max 4 columns

# What?
### mobile
![mobile](https://cloud.githubusercontent.com/assets/31692/3738403/6ac26bd4-1740-11e4-910a-df0bd1e9127b.png)

### desktop
![desktop](https://cloud.githubusercontent.com/assets/31692/3738402/6ac14790-1740-11e4-8333-25a19ddb8987.png)

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![Illusions](http://static.paulboxley.com/2014/monument_valley_penrose.gif)
I think it is just very flexible by design, you can see the [data structure here](https://github.com/guardian/frontend/blob/master/facia-tool/public/javascripts/modules/vars.js#L13). It's just an array which we use the index to get the content.

Looping @stephanfowler to get an insight on whether this was left intentionally vague?