Highlight lines from first non-whitespace char

Only highlight from the beginning of the line.

# Current state

![Highlighting the complete line](https://f.cloud.github.com/assets/224922/37393/e87e740a-5441-11e2-86b2-56357c4de223.png)

# With this branch

![Highlighting from beginning of indentation](https://f.cloud.github.com/assets/224922/37401/a624b434-5446-11e2-8927-35b02c43ca52.png)

Inviting @ptrv and @wyuenho to discuss this change.