Merge pull request #2 from crustyjuggler/select-product

added test to check the display after an unsuccessful vend

added code and test to display PRICE and price of product if not enought money is inserted

added code and test to change the display after vending THANK YOU is displayed

added test and code to vend item if enought money is inserted. minor refactoring

refactored tests and code

added code to actually check if a product is available

added initial test for selecting products

Merge pull request #1 from crustyjuggler/accept-coins

checked that total is being calculated as expected and added a currency formatter

refactored to use Display function - added test for INSERT COINS display

modified test because it was not testing what it is supposed to be testing

added test for display and refactored app to accept or reject coins properly

added check for invalid coins and modified tests to pass coin

added ability to accept valid coins