A vector of filenames for downloaded hierarchy pages
output
Detail will return a data frame with each taxon and their taxonomic
synonyms; counts will return a dataframe with each species and synonym counts.
Value
When output is set to detail, it returns a data frame where each row is the
taxonomic unit that has a synonym, the hierarchy ID, and the synonym.
When output="counts", each taxon is included whether it has a synonym or not.
Rather than report the synonyms, it reports the number of synonyms for each.