RotatePins uses modulus (%) to avoid over-rotating, but the order of
operations was wrong:

initialRotation + newRotation % 6

instead of

(initialRotation + newRotation) % 6

In some cases, this could lead to creation of pin index numbers that
were larger than the number of pins.

If the sum of the current rotation state and the additional rotation
exceeds 6, the old rotatePins function would over-rotate. The unit
test was modified to induce this situation, where a 4 x 60 degree
rotation is applied to a block that has already been rotated 4 x 60. In
this case, the old rotatePins would calculate a rotNum of 8, which would
make some pin indexes incorrect.