A typical GFF file which should be stored in a folder (for example in "GFF").
This folder is the input for the readData(...,gffpath="GFF")
function.
The corresponding FASTA file is stored in the "data" subdirectory
of the PopGenome package. It has to be stored in a folder with the
SAME NAME as the GFF file (for example in "FASTA").
readData("FASTA", gffpath="GFF")