fixed pysam backward compatibility issue (0.8.3, 0.9)
fixed pysam backward compatibility issue (0.8.3, 0.9)

kundajelab/atac_dnase_pipelines,kundajelab/atac_dnase_pipelines,kundajelab/atac_dnase_pipelines,kundajelab/atac_dnase_pipelines,kundajelab/atac_dnase_pipelines