Fix thema selector on small screen (only DESKTOP)


Simpler solution makes the list of topics responsive.

Fix #700 

TABLET size:

![tablet](https://f.cloud.github.com/assets/621420/1483375/5dea8b96-46f6-11e3-82b3-d93b477e80f5.png)



PHONE size:

![phone](https://f.cloud.github.com/assets/621420/1483379/76ba1f06-46f6-11e3-8811-a05d9995ad78.png)