refactoring slice_fasta_to_exons
refactoring slice_fasta_to_exons

slice_fasta_to_exons just returns the array of gene alignments.
more generically, slice_fasta_from_genbank_file does the same for any
type of locus.

TheMolecularEcologist/phylogenomics,daisieh/phylogenomics,daisieh/phylogenomics,TheMolecularEcologist/phylogenomics,daisieh/phylogenomics,TheMolecularEcologist/phylogenomics