Working version for making a selection and quantity

user_input file:
 1) contains all user input methods
 2) methods to prompt user to make selection and quantity
 3) methods to gets and change to float or keep as string

cash_register3 file:
 1) anything related to calculations and creation of hash
    with quantity and subtotal per item
 2) displayTransactionOptions method that displays the menu of items
 3) calculate subtotal method
 4) return a hash from the array of hashes
    (that only has 1 specific item's information)