Change pickMove() recieve only  opponent's last move.

The goal was to simplify code in the Player classes. By sending only
one parameter, the opponent's last move, the players are spared the
task of parsing the history array. Furthermore, they do not need to
have PlayerNum as an instance variable, and thus a no-args constructor.
On the first move, the chooseCorD() method sends an empty string.

Also updated method and variable names:
- pickMove() became chooseCorD(String opponentsLastMove)
- Player interface became PDPlayer

Algorithm updated to a true round-robin where each player only plays
each other once instead of twice.
Remove .class files from repository
Use reflection to dynamically load player classes.
Dynamic class Loader working.
Update package.bluej
Add PlayerTester class.

PlayerTester is a utility for students to test their PDPlayer classes
before they submit them. The PlayerTester creates multiple instances
of their player class and runs a 200 iteration game of Prisoner's
Dilemma against them to see that they will not crash the PDTournament
application. Basically, it verifies that they can instantiate objects
from their class and that their chooseCorD() method will always return
a "c" or "d" when called.

Use the PlayerTester by changing line 12 to reflect the name of the
player class you are testing. It currently reads:
   PDPlayer player = new BrokenPlayer1();
Simply replace "BrokenPlayer1()" with the name of your class.

The test occurs by calling the chooseCorD method for NUMROUNDS number
of times (default is 200). Each time it sends a randomly selected "c"
or "d" as the argument for "opponentsLastMove". The default number
of instances is 10, but this could be increased to 1000 or more to
verify code whose behavior hinges upon  particular sequences in the
opponent's moves.

Also added BrokenPlayer1 class, which returns "e" instead of "c" or
"d".
Improve terminal output. Fix bug.

Player class names are outputted instead of "player0" and "player1".
Also, when tournament concludes, the author names and class names
of the top three scorers are printed.

Fixed bug in PDDriver, where classes that did not implement the
PDPlayer interface were removed from playerList.

Added another test class, "BrokenPlayer2", which does not implement
the PDPlayer interface, and thus gets removed from the playerList.

This version should be adequate for classroom use.