fix images in floating text for heise RSS feed


![heise-feed-before](https://cloud.githubusercontent.com/assets/245432/3810849/82e1baa2-1c96-11e4-8a82-73b0d5fb97a5.png)

After
![heise-feed-after](https://cloud.githubusercontent.com/assets/245432/3810843/6c2f0df0-1c96-11e4-9d2a-cc6418deee81.png)