Dumps output from jellyfish count into a human-readable format.
    :param mer_file: Output from jellyfish count.
    :param output_file: Where to store output. Default counts.fasta
    :param options: Other options to pass to jellyfish. Input should be a string, with options typed as they would be
    on the command line.
    :param returncmd: If set to true, function will return the cmd string passed to subprocess as a third value.
    :return: Stdout and stderr from calling jellyfish.

def dump(mer_file, output_file='counts.fasta', options='', returncmd=False):
    """
    Dumps output from jellyfish count into a human-readable format.
    :param mer_file: Output from jellyfish count.
    :param output_file: Where to store output. Default counts.fasta
    :param options: Other options to pass to jellyfish. Input should be a string, with options typed as they would be
    on the command line.
    :param returncmd: If set to true, function will return the cmd string passed to subprocess as a third value.
    :return: Stdout and stderr from calling jellyfish.
    """
    cmd = 'jellyfish dump {} -o {} {}'.format(mer_file, output_file, options)
    out, err = accessoryfunctions.run_subprocess(cmd)
    if returncmd:
        return out, err, cmd
    else:
        return out, err