In this implementation of the ISet interface the elements in the Set are
maintained in ascending order.
The data type for E must be a type that implements Comparable.
Students are to implement methods that were not implemented in AbstractSet
and override methods that can be done more efficiently. An ArrayList must
be used as the internal storage container. For methods involving two set,
if that method can be done more efficiently if the other set is also a
SortedSet do so.