o remove non-ASCII fancy quotes
 o use Rd macros for code and links
 o make a specific import from OAIHarvester
 o remove trailing white space
 o change \dontrun to \donttest
roxygenise the documentation in light of changes to pg_list_records.R
Merge pull request #28 from gavinsimpson/fix-pg-list-records

Fixes to `pg_list_records.R`