Takes a multifasta file and returns a list of sequence names
        :param contigsfile: multifasta of all sequences
        :return: list of all sequence names

def sequencenames(contigsfile):
        """
        Takes a multifasta file and returns a list of sequence names
        :param contigsfile: multifasta of all sequences
        :return: list of all sequence names
        """
        sequences = list()
        for record in SeqIO.parse(open(contigsfile, "rU", encoding="iso-8859-15"), "fasta"):
            sequences.append(record.id)
        return sequences