Write a heapSort method that takes an array of type Comparable
and sorts the array.  It should use the CompareTo() to compare
two elements of the array.  The heapSort method should look like:

public void heapSort(Comparable[] 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.