Write a heapSort method that takes an array of ints
and sorts the array.  he heapSort method should look like:

public void heapSort(int[] arr) {
	buildHeap(arr);
	sortHeap(arr);
}

You will almost certainly find it easier to do this if you
have a method called adjust() which will help an element trickle
down from the top of the heap to its appropriate position.