Fix post highlighting

Before:

![before](https://cloud.githubusercontent.com/assets/31063/2547875/8ab48bdc-b658-11e3-8958-1987db9f00a8.gif)
![before_reg](https://cloud.githubusercontent.com/assets/31063/2547876/8ab5ced4-b658-11e3-9f07-0a13a6715f4f.gif)


After:

![after](https://cloud.githubusercontent.com/assets/31063/2547880/92c54d70-b658-11e3-80e9-99bfa11b3345.gif)
![after_reg](https://cloud.githubusercontent.com/assets/31063/2547879/924e2984-b658-11e3-9d70-edcf3ac3835c.gif)