Java Classwork #5 (DiceRoll)
05) Create a non-static class named 'DiceRoll' in its own file.  The class
    should contain a single constructor that takes two positive integers as its
    arguments, representing the number of sides of two separate fair dice.
    For example, a call such as

       DiceRoll dice = new DiceRoll(6, 10);

    will create a new DiceRoll object called 'dice' that will set up a six-sided
    die (numbered 1 through 6) and a ten-sided die (numbered 1 through 10).

    Remember that the above call to 'DiceRoll' is an example.  No specific dice
    values should appear anywhere in the 'DiceRoll' class.  The one exception
    to this is if a non-positive integer is submitted to either the constructor
    or the 'changeDice' method.  Any die assigned a non-positive number of sides
    should instead be made into a six-sided die.

    The method 'main' and the keyword 'static' must not appear anywhere in the
    'DiceRoll' class.  Make sure all of the internal variables in the 'DiceRoll'
    class are private.  The class should contain the following public methods:

       newRoll
          Arguments:  None
          Actions:    "Rolls" both dice and stores the result of the rolls
          Displays:   Nothing
          Returns:    Nothing
       -------------
       lastRoll
          Arguments:  None
          Displays:   Nothing
          Returns:    A string containing BOTH of the die values from the last
                      (most recent) time that the dice were rolled; the string
                      should have the form "#, #" (e.g., "2, 9", but without the
                      quotes); if this method is called before the current dice
                      have been rolled for the first time (or right after the
                      'reset' method has been called), an empty string should be
                      returned
       -------------
       sum
          Arguments:  None
          Displays:   Nothing
          Returns:    An integer equal to the sum of the most recent roll of the
                      two CURRENT dice; if the dice have not yet been rolled (or
                      if the 'reset' method has just been called), a zero should
                      be returned
       -------------
       total
          Arguments:  None
          Displays:   Nothing
          Returns:    An integer equal to the sum of ALL of the rolls so far of
                      the two CURRENT dice; if the dice have not yet been rolled
                      (or if the 'reset' method has just been called), a zero
                      should be returned
       -------------
       reset
          Arguments:  None
          Actions:    Resets the internal "sum" and "total" dice values to zero,
                      and also clears the internal 'last roll' values of the dice
                      (as if the current dice have never been rolled)
          Displays:   Nothing
          Returns:    Nothing
       -------------
       changeDice
          Arguments:  Two positive integers representing the number of sides of
                      two separate fair dice
          Actions:    Changes the number of sides of the two dice to the newly
                      supplied values; also calls the 'reset' method to clear
                      all internal sum values and the roll history
          Displays:   Nothing
          Returns:    Nothing


ADVANCED OPTION #1 FOR CLASSWORK #5
    To the 'DiceRoll' class, add another public method named 'cheatRoll' that
    functions in the same manner as the 'newRoll' method, except that for each
    die, regardless of the number of sides on the die, it should be twice as
    likely that an even number (as opposed to an odd number) will be rolled.

ADVANCED OPTION #2 FOR CLASSWORK #5
    To the 'DiceRoll' class, add another public method named 'showLastRoll' that
    functions in the same manner as the 'lastRoll' method, except that it returns
    nothing, but instead displays a JFrame containing the two values of the most
    recent dice roll.  It is up to you how you display the two values on the
    JFrame (text in labels, graphically with images, large dots, etc.).