added documentation
added documentation

pysam-developers/pysam,TyberiusPrime/pysam,TyberiusPrime/pysam,brendanofallon/pysam,daler/pysam,kyleabeauchamp/pysam,bioinformed/pysam,daler/pysam,brendanofallon/pysam,pysam-developers/pysam,bioinformed/pysam,carolinux/pysam,kyleabeauchamp/pysam,TyberiusPrime/pysam,bioinformed/pysam,mattions/pysam,daler/pysam,carolinux/pysam,dannon/pysam,TyberiusPrime/pysam,brendanofallon/pysam,mattions/pysam,daler/pysam,mattions/pysam,carolinux/pysam,brendanofallon/pysam,pysam-developers/pysam,dannon/pysam,pysam-developers/pysam,mattions/pysam,bioinformed/pysam,daler/pysam,dannon/pysam,carolinux/pysam,carolinux/pysam,bioinformed/pysam,dannon/pysam,kyleabeauchamp/pysam,TyberiusPrime/pysam,kyleabeauchamp/pysam,mattions/pysam,kyleabeauchamp/pysam,brendanofallon/pysam,dannon/pysam