Optionally hide the absolute path in HTML reports

![before](https://cloud.githubusercontent.com/assets/3754439/2814975/30e2c088-ceb3-11e3-8ba7-6dd8edb03484.png)
![after](https://cloud.githubusercontent.com/assets/3754439/2814974/30e16fb2-ceb3-11e3-8171-52584f723cca.png)