The stub of append() should look like this:
   void ArrayQueue::append(const Item& it) {
The append() method should behave as follows:
  1. If the queue is full, throw a FullQueueException;
  2. Otherwise:
    1. Set myLastIndex to (myLastIndex + 1) modulus myCapacity; and
    2. Store it in myArrayPtr at index myLastIndex;
    3. Add 1 to mySize.