Removing un-needed padding for fluid 250 ads

This removes extra padding from responsive banner ads on the widest breakpoint.

Before;

![screen shot 2014-12-17 at 16 55 24](https://cloud.githubusercontent.com/assets/1303616/5475127/34c22e38-860e-11e4-8242-0d4687b630d0.png)


After;

![screen shot 2014-12-17 at 16 55 47](https://cloud.githubusercontent.com/assets/1303616/5475131/39b47342-860e-11e4-898c-7ab00d6058fc.png)