updated use case document

Hi - I just wanted to advertise that the use case document<http://w3c.github.io/csvw/use-cases-and-requirements/> is now updated with Use Case #4 - Publication of public sector roles and salaries<http://w3c.github.io/csvw/use-cases-and-requirements/#UC-OrganogramData> and Use Case #5 - Publication of property transaction data<http://w3c.github.io/csvw/use-cases-and-requirements/#UC-PublicationOfPropertyTransactionData> ... plus a number of other minor changes. Comments welcome.

Jeremy