removed NCBI2R dependency
getfullhierarchyfromtsn returns no factors
tax_names accepts multiple ranks to query
tax_name accepts vectors as input
Merge pull request #118 from EDiLD/dev_tax

improvements of tax_name
tax_name has an option to query both, NCBI and ITIS, in one call and return the union of both
Merge pull request #119 from EDiLD/dev_tax

last fix for  Issue #117