line-highlight fix + pygments highlight

- fix line highlight that was off by 1
- when pygments available, try to highlight
- when lines have no generated code, do not genera the subdiv and do not
  make clickable
- line number with at least 3 digit for alignment of code
- line that can be expanded with + in front

![capture decran 2014-04-27 a 13 19 13](https://cloud.githubusercontent.com/assets/335567/2811192/8c9cf55c-ce0d-11e3-8c7b-8491a7350c9d.png)