Fixes border radius when selecter opens above

Before:
![screen shot 2014-07-23 at 6 58 05 pm](https://cloud.githubusercontent.com/assets/1996521/3681588/e939d2fa-12bc-11e4-84c2-03b7899c65d7.png)

After:
![screen shot 2014-07-23 at 6 58 33 pm](https://cloud.githubusercontent.com/assets/1996521/3681590/f04d9054-12bc-11e4-8ed4-7f10556e2575.png)