Update base search function to not crash when a single result is returned
Update tests
update comment to reflect base
Allow invoices to search by customer_id
Search for unpaid invoices
Merge pull request #1 from jer-k/start-some-work

Update search to work when single record is returned
Add client error
require errors
Remove error code from base
remove find_by in collection for now
Add search for multiple on invoice
Tests
raise exceptions
Merge pull request #3 from jer-k/search-unpaid-customers

Search unpaid customers invoices
bump version