writes contents of stats to outname_diff_stats.csv
    :param stats:
    :param options:

def write_diff_summary(stats, options):
    """
    writes contents of stats to outname_diff_stats.csv
    :param stats:
    :param options:
    """
    # set output file name
    out_name = '%s_diff_stats.csv' % options.outname
    filename = os.path.join(os.getcwd(), out_name)

    # open file & create csv writer object
    f = open(filename, 'w')
    statswriter = csv.writer(f)

    # write header
    statswriter.writerow(stats['header'])

    # write auc
    line = ['AUC']
    for metric_tup in stats['AUC']:
        try:
            len(metric_tup)
            line.append('[%0.2f, %0.2f]' % (metric_tup[0], metric_tup[1]))
        except:
            line.append('%0.6f' % metric_tup)
    statswriter.writerow(line)

    # write enrichment factors
    for title in [x for x in sorted(stats.keys()) if 'E' in x]:
        line = [title]
        for metric_tup in stats[title]:
            try:
                len(metric_tup)
                line.append('[%0.2f, %0.2f]' % (metric_tup[0], metric_tup[1]))
            except:
                line.append('%0.12f' % metric_tup)
        statswriter.writerow(line)