see #11 for details:

@boussau:
> model with codon positions: iqtree -s orf1a_b_cds_NT_OK.fst -spp partitionFile.nex where partitionFile.nex contains :
>
> #nexus begin sets; charset part1 = 1-23070\3; charset part2 = 2-23070\3; charset part3 = 3-23070\3; charpartition mine = GTR+R:part1, GTR+R:part2, GTR+R:part3; end;
>
> where 23070 is the total size of the alignment It's a model that is a bit parameter rich, so don't use it on single gene alignments.
>
> For amino acids, I'd do: iqtree -s orf1a_b_cds_prot_OK.fst -m LG+F+R
>
> And for codons: iqtree -s orf1a_b_cds_NT_OK.fst -st CODON1 -m ECMK07+F