Fixed calculator layout for pre-L

The calculator buttons were small in Kitkat, fixed it to fit the layout.

Old
![device-2014-10-25-144257](https://cloud.githubusercontent.com/assets/866735/4779037/b670b0d8-5c12-11e4-83d0-b6a2c5cf90a8.png)

New
![device-2014-10-25-144321](https://cloud.githubusercontent.com/assets/866735/4779038/b95a6924-5c12-11e4-8970-f494b84d1b84.png)
Ah OK, we can leave it I suppose.