character string; NULL to use response service type or "csv" or "xml" to force that format
clean_dates
boolean; whether to clean date/time columns
rename
boolean; whether to rename column headings (they are usually blank from the API)
warn_on_initial_parse
logical; should warning messages be shown during the orignal attempt at parsing the response? The default is FALSE
as many of the data items need further cleaning and so the warning messages from the original attempt to parse the file are uninformative.