did NOT handler history record properly

[hughgr]

thanks for sharing such a wonderful plugin, but the code handle history record do NOT work properly.

 if (toStackIndex > -1) {
            direction = toStackIndex > fromStackIndex ? DIRECTION.FORWARD : DIRECTION.BACK;
    } else {
            direction = DIRECTION.FORWARD;
            stack.push(toPath);
            sessionStorage.setItem(HIS_KEY, JSON.stringify(stack));
          }

for example if I
A->B1->C
then i back to A, the history record stack still remains [A,B1,C]
then i go to B2, the stack was like [A,B1,C,B2],
then i move to C, oops, the C was in record and index is smaller then B2
so we get "back" instead of "forward"