Add merchant relationships
Add invoice_item relationships

* require big-decimal in file loader

* convert unit price to big-decimal
Add item_repository relationships

* Convert unit price to big decimal
Refactor tests to use BigDecimal

* All minitest tests passing

* 25/50 spec_harness passing
Rubocop style fixes

* Single quotes

* Excess blank line at end of class
Add CodeClimate Badge
Merge pull request #55 from trayo/39_add_relationships

39 add relationships