fix raw_input CSS

I had to express padding in px, not em for consistent appearance. I'm not sure why.

closes #5324
before:
![screen shot 2014-03-10 at 3 16 05 pm](https://f.cloud.github.com/assets/27600/2379924/ab94f1f8-a8a1-11e3-8e79-cff91832fb61.png)

after:
![screen shot 2014-03-11 at 16 08 31](https://f.cloud.github.com/assets/151929/2392050/1e00318c-a972-11e3-8e3c-9f67954f258a.PNG)