Adjust superscript to center and avoid overlap

It was overlapping for me:
![2014-10-13 10 27 11](https://cloud.githubusercontent.com/assets/69736/4614923/10cc4bbe-52e5-11e4-802d-ae146a9bd643.png)


What about this:
![2014-10-13 10 25 46](https://cloud.githubusercontent.com/assets/69736/4614918/fa8751c8-52e4-11e4-9802-e905e500af76.png)