Add a failing test for Topping.initialize.
Add a passing initialize method
Add a failing vegetarian optional argument
Add a passing vegetarian keyword argument
Add failing Pizza .initialize method
Add passing test for .initilaize method in Pizza class
Add failing test for default value of cheese in Pizza class
Add passing test for deafult value of cheese
Add failing test for vegetarian? method
Add passing test for vegetarian pizza
Add failing test to add topping to existing pizza instance
Add passing test for adding topping
Add passing test for delivery! and late?
Add delivery method