Star ratings rendering fix

Minor issue, the star ratings rendering on Safari Version 7.0.5 (9537.77.4) (Mac OS) contains a set of 5 small dots at the bottom (see bellow).
This fix removes them by applying 1px padding within the star sprites.

@kaelig, do you reckon images can  be further optimised for smaller size?

### before
![screen shot 2014-07-25 at 11 41 20](https://cloud.githubusercontent.com/assets/1492162/3700946/fc275022-13e8-11e4-98a5-c807508adb24.png)

### after
![screen shot 2014-07-25 at 11 41 34](https://cloud.githubusercontent.com/assets/1492162/3700945/fc257af4-13e8-11e4-825c-834acecb8687.png)