Minor change in widgets.less to fix alignment issue

When aligning certain widget in an hbox, you would get this
![un-aligned](https://cloud.githubusercontent.com/assets/2397974/4601268/27d317b6-50f6-11e4-9dfa-6d6856978d6a.png)

With this change:
![aligned](https://cloud.githubusercontent.com/assets/2397974/4601276/83cb3152-50f6-11e4-9042-03e4570d6d8c.png)
@jdfreder