The TARIC Validator ROIMB4 should use the regulation_group_id not iod

This validation is trowing validation errors because it is using the
wrong key to look to the RegulationGroup
Add note to README about audit:verify for validators
Merge pull request #195 from alphagov/fix-ROIMB4-validator

The TARIC Validator ROIMB4 should use the regulation_group_id not iod