taxize v0.7.8

MINOR IMPROVEMENTS

• Fix to iucn_summary() (#543) thanks @mcsiple
• Added message for when too many Ids passed in to ncbi_get_taxon_summary()
  suggesting to break up the ids into chunks (#541) thanks @daattali
• Fix to itis_acceptname() to accept multiple names (#534) and now
  gives back same output regardless of whether match found or not (#531)

BUG FIXES

• Fix to tax_name() for some queries that return no classification data
  via internal call to classification() (#542) thanks @daattali
• Another fix for tax_name() (#530) thanks @ibartomeus
• Fixed docs for rankagg() function, use requireNamespace() in examples
  to make sure user has vegan installed (#529)