.unstyled -> .u-unstyled

Some of the templates were still using the non-prefixed version of the `unstyled` helper. This PR renames them into `u-unstyled`.

## Before

![screen shot 2014-04-14 at 11 08 55](https://cloud.githubusercontent.com/assets/85783/2693973/e3f5ffde-c3bc-11e3-8168-626177060797.PNG)


## After

![screen shot 2014-04-14 at 11 09 09](https://cloud.githubusercontent.com/assets/85783/2693975/e739c144-c3bc-11e3-9192-18e8f370b8e0.PNG)

![ ](http://media.giphy.com/media/rW5uNVaLIg0zC/giphy.gif)