Make the dropdown login buttons are responsive for small device.


![screen shot 2014-08-05 at 12 46 45 am](https://cloud.githubusercontent.com/assets/1086008/3800398/edb6ce3e-1bf7-11e4-826f-208d41322bca.png)
![screen shot 2014-08-05 at 12 46 04 am](https://cloud.githubusercontent.com/assets/1086008/3800402/f26a8a74-1bf7-11e4-8cfe-359ca2dcf907.png)

Signed-off-by: Jia-He Jou <joujiahe@gmail.com>