Added new color for 'D' state.

As a system administrator who deals with network-attached storage units, I often find myself looking for processes in state D to find out where performance issues come from.

I opted to color the state in such processes to distinguish them from the other states. It doesn't look intrusive, and in a normal situation, it shouldn't happen often.

This is what it looks like with this commit:
![2014-10-14-024002_252x170_scrot](https://cloud.githubusercontent.com/assets/887736/4622932/474ae64c-5343-11e4-85f8-3ad7d88e3829.png)

Thank you!