added fix for issue 43
added fix for issue 43

--HG--
branch : dev-0.4

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