Make in-text calls to actions more obvious

This PR improves accessibility of in-text calls to action, making them more obvious (a blue link being barely visible when inside a context of dark text).

Has an impact on discussion and identity only.

![screen shot 2014-03-24 at 14 49 25](https://f.cloud.github.com/assets/85783/2500543/8923f46c-b363-11e3-8711-3bdb09b22d86.PNG)

![screen shot 2014-03-24 at 14 36 29](https://f.cloud.github.com/assets/85783/2500550/93b27a66-b363-11e3-9adf-930962d1ab14.PNG)

![ ](http://media1.giphy.com/media/kMkHbjHIIhiMw/200.gif)