Fix styling of series labelling

#### Before
![screenshot from 2014-04-09 10 48 08](https://cloud.githubusercontent.com/assets/80089/2654315/3185669e-bfd1-11e3-8f45-e0c4d056909e.png)

#### After
![screenshot from 2014-04-09 10 47 57](https://cloud.githubusercontent.com/assets/80089/2654313/2ffd099e-bfd1-11e3-9d54-289cb8843794.png)