Nest Octicon customization for slides only

Fixes "oops" of specialized style for Octions on slides applying side-wide.

![screen shot 2014-12-30 at 10 50 50 pm](https://cloud.githubusercontent.com/assets/352082/5585809/5b8c82e4-9076-11e4-8a63-3dd9a028109f.png)