Function sub

sub(a, b, dst?): Quat
Subtracts two quaternions.
Parameters
- a: Quat
  Operand quaternion.
- b: Quat
  Operand quaternion.
- Optional dst: Quat
  quaternion to hold result. If not passed in a new one is created.
Returns Quat
A quaternion that is the difference of a and b.