A Stock Item

Design a class named StockItem that can be used to keep track of items in stock
 at a store. Each stock item object must include the following:

• the item name
• a price 
• the quantity of the item that is currently in stock

When a StockItem object is created, the object must be constructed with a 
name, a price, and a current quantity.  (only 1 constructor)


Operations on a stock item include the 
following:

• retrieve the description of the item
• retrieve the price of the item
• retrieve the quantity of the item that is currently in stock
• set a new price for the item
• remove some quantity of the item from the quantity in stock
• add some quantity of the item to the quantity in stock

Write the StockItem class