Cast values to Strings when generating CSV rows

node-csv automatically converts Dates to their timestamp values for some
reason, so we cast them to Strings before hand so that they render
correctly in the CSV files (not as large numbers, which Excel renders in
standard form)
Also check type of value as we convert that too
Date comparison test ignores timezone to be cross machine compatible
Merge pull request #242 from unepwcmc/csv-date

Cast values to Strings when generating CSV rows