Cleanup: Fix broken javadoc

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Merge pull request #64 from iZettle/fix-javadoc-compilation-errors

Cleanup: Fix broken javadoc
Cart: Utility library for handling items added to a cart

Facilitating vat and discount calculations
Cart: Refined implementation for handling disounts properly

Distributing remainder or excess discount to minimize total rounding
error and effectively gurantee that exactly the total discount is
distributed over all line items.
Cart: Making proper assertions in 2 tests

Instead of a couple of System.out that where development remnants