Bug fix: Missing require when generating genbank output for BioSQL sequence

 * Bug fix: Missing require when generating genbank output for BioSQL
   sequence. Partly fix https://github.com/bioruby/bioruby/issues/89
Bug fix: Only do gsub on bio_ref.reference.authors if it exists.

 * Bug fix: Only do gsub on bio_ref.reference.authors if it exists.
   Fix https://github.com/bioruby/bioruby/issues/89