Add ad slot below container's 'show more' button

We now add two container slots
 
 * one for tablet+ which is placed in the ad slice
 * one for mobile that is placed after the container

![screen shot 2014-10-28 at 23 22 30](https://cloud.githubusercontent.com/assets/74132/4818873/52d018b8-5ef9-11e4-8893-b31831080ef0.png)