isUnique

  Write a static method isUnique that takes an array of
   integers as a parameter and that returns a boolean value indicating whether
   or not the values in the array are unique (true for yes, false for no).  The
   values in the list are considered unique if there is no pair of values that
   are equal.  For example, if a variable called "list" stores the following
   values:

        (3, 8, 12, 2, 9, 17, 43, -8, 46, 203, 14, 97, 10, 4)

   then the call:

        isUnique(list)

   should return true because there are no duplicated values in this list.  If
   instead the list stored these values:

        (4, 7, 2, 3, 9, 12, -47, -19, 308, 3, 74)

   then the call should return false because the value 3 appears twice in this
   list.  Notice that given this definition, a list of 0 or 1 elements would be
   considered unique.

   Write your solution to isUnique below.