Added a failing test for Topping.initialize.
Topping test now works.
Failing test for vegetarian option
Updated Topping class to incorporate vegetarian pizza
Added topping test for Pizza class.
Created an initialize method for the Pizza class. Adds an array of toppings or empty array if no toppings.
Added test for automatic input of 'cheese' if no toppings are added.
All tests passed. Pizza.toppings initializes to ['cheese'] if no arguments are passed.