very minor. Changed a comment line in phyloseq()

Need to extend the meaningless quotation-mark removal from just the
phylogenetic tree tip names to all taxa_names in all components. It is
fast, even on HMP dataset 45000 OTU names. Not even worth checking for
them first, just run fixed-gsub on all components.
Will need to define a taxa_names()<- assignment S4 generic. Maybe keep
it internal, since you don't really want users assigning name changes
to components willy-nilly