日付のラベルが改行してしまうのを回避

## before
![screen shot 2014-05-16 at 9 11 40 pm](https://cloud.githubusercontent.com/assets/823185/2996638/6a560d04-dcf3-11e3-835c-ed960558f146.png)

## after
![screen shot 2014-05-16 at 9 11 47 pm](https://cloud.githubusercontent.com/assets/823185/2996640/6e2628ec-dcf3-11e3-8f79-920974c8081d.png)