More design updates.
initial commit of the ProductType enumeration
Adding updates from design change.
checking in unit test for Product class
Added constant tax rates and decima formatter to product class design.
Implemented method bodies for the Product class
Added total price to Product class design. Added getters for total price and sales tax to Product class design.
Updated class based on design updates. Added total price field. Added getters for total price and sales tax. Added rounding to sales tax computation. Added more tests to Product unit test.
Added size method, and getters for total tax and total price to ShoppingCart class design.
Removed print outs.
Added test cases to ShoppingCartTest
Modified visibility of DecimalFormatter in Product class design.
Implemented ShoppingCart method bodies.
Updated logic in Product class to round UP to the nearest 0.05
Added/Updated JavaDoc comments.