Fix id check; add method to add filters
Fix id check; add method to add filters

pysam-developers/pysam,pysam-developers/pysam,kyleabeauchamp/pysam,bioinformed/pysam,kyleabeauchamp/pysam,bioinformed/pysam,pysam-developers/pysam,kyleabeauchamp/pysam,bioinformed/pysam,kyleabeauchamp/pysam,bioinformed/pysam,kyleabeauchamp/pysam,bioinformed/pysam,pysam-developers/pysam