Remove unnecessary padding when a sidebar teaser doesn't have an image

Both the heading and body in a sidebar teaser have content containers, but when there's no image it leaves a big gap between the two. This removes the top padding on the content, so:

![image](https://cloud.githubusercontent.com/assets/1784740/2800567/91bbf3c4-cc75-11e3-9aaf-34a5495af5c5.png)

becomes:

![image](https://cloud.githubusercontent.com/assets/1784740/2800574/a07de9bc-cc75-11e3-95b5-6111a018e13b.png)