Add happy_discount method
Update happy_discount setter method
happy_hour? method
Add get price method
Add Date requirment to happy hour
Update test for Monday or Wednsday happy hour
Add failing test for exempt drinks
Add failing test for exempt drinks
Add exempt drink criteria
add failing test for purchases
Add select_drink method
add total_purchases
add failing test for most popular drink
Add method for most popular drinks
wrote failing test for discount_for_day
Add discount_for_day method / update get_price method
add failing test for update discount
Add update discount method
Add failing test for unique discount
Add method unique_discount