better error message for out-of-range tid
better error message for out-of-range tid

--HG--
branch : dev-0.4

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