Handle soundcloud.com links. 

#172

![screen shot 2014-01-21 at 11 34 25 am](https://f.cloud.github.com/assets/2622152/1962108/f9c4ff94-8281-11e3-8fe1-77ffd6664b7a.png)

![screen shot 2014-01-21 at 11 44 02 am](https://f.cloud.github.com/assets/2622152/1962110/f9f6f986-8281-11e3-91b8-acce37b607d4.png)