Edit distance markers

Changed the look of distance markers. Make sure that OpenSans-Light font is loaded in css (see examples/HoleDrawing.html)

![screenshot 2014-06-13 17 18 49](https://cloud.githubusercontent.com/assets/2392131/3273885/a66f0baa-f329-11e3-8ed1-c1e6398472c0.png)