added the discount calculator test class
created the discount calculator module with the DiscountCalculator class
added the discount calculator module
added a function to test for 15 percent
modified the calculate function to perform generic discount calculations
Added function to test for dollar type discounts
modified the dollar function to accept absolute amounts
added if/else logic to calculate function
added test for invalid discount type
added tests to test for floating point inputs
added function to test excess discount
added if/else logic to test for excess percentage and absolute values