Zero top and bottom margins for live blog thumbnails or captionless pics

Before (an image which is both captionless and thumbnail):
![screen shot 2014-12-01 at 10 59 43](https://cloud.githubusercontent.com/assets/4549425/5244585/c50323bc-7948-11e4-9947-83bf66682b7a.png)

After:
![screen shot 2014-12-01 at 10 58 32](https://cloud.githubusercontent.com/assets/4549425/5244576/ad5c1890-7948-11e4-9c1c-570404412024.png)