Lab 2

Take the generic binary tree class that we developed.  Use it to create an 
animals program.  The program should ask the user to think of an animal.
It should then ask a series of yes or no questions to attempt to identify the
animal.  If it succeeds, offer to play again.  If it identifies the wrong
animal, ask the user to enter a yes or no question to distinguish between the
identified animal and the correct animal.  Modify the data base to accomodate
the new animal.

You will use a tree with questions in the internal nodes and animals in the
leaf nodes.  Each time a new animal is encountered, you should put the new
question into the node containing the name of the wrongly found  animal,
then put the wrongly found  animal in the left child and the new animal in the
right.

If you find that BT.java needs more functionality than it has, create
a sub class, AnimalTree extends BT, and add methods to it.