create invoice_items class and tests
create invoice_items class, repo, tests, and test data
Merge branch 'master' into srt-invoice-items
Merge pull request #22 from srt32/srt-invoice-items

Finish invoice_items, class, repo... refactored...
updated transaction_repo so that 'result' worked
updated transaction_repo so that 'result' worked
Merge branch 'master' into transaction_repo