ZCalc - A simple calculator.

This program was written just to practice some python.
It is a simple calculator with a GUI that allows a user to do math.

Everything should be fairly self explanetory in this program.  Click
on the number buttons to input a number then choose an operator.
Click the number buttons to enter the second number and press '='
to calculate the answer.

There is no delete button in the main app.  However, pressing the 'Delete'
button on the keyboard causes the last digit to be removed from the entry
and thus the calculation.