issue 17 - added unit test catching missing file for pysam.index
issue 17 - added unit test catching missing file for pysam.index

--HG--
branch : dev-0.4

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