Added RedRunner project.

This paints a long monochrome (red) trail of about 16 pixels that moves along the LED-strip similar to the RunningColorDot. The brightness of the trail is corrected for non-linear luminance perception (based on CIELAB models). This is the first step in the project, more additions are to follow.

Also improved an explanation on the RunningColorDot code.
Added barriers to the RedRunner demo.

Every 150ms, there is a one in four chance of a barrier appearing. These barriers interact with the running trail: whenever the trail runs into a barriers, the direction of the trail changes. The barrier also loses 'structural integrity' (brightness) as a result of the collision. After 4 collisions the barrier is destroyed (no longer lit up) and no longer interacts with the trail.