weird behavior of phyndr_taxonomy

[wcornwell]

@mwpennell @richfitz If you pass in a taxonomy matrix without rownames, phyndr_taxonomy just returns the tree that you passed in.

This gets confusing because you have to specify taxonlookup::lookup_table(...by_species=TRUE) to create the taxonomy or else nothing works and there is no informative error message.

Should we change this in phyndr or in taxonlookup or both ?