clarified no-index behavior in bam multi reader
clarified no-index behavior in bam multi reader

sksaskrobinsons/code,kdmurray91/bamtools,domibel/bamtools,boratonAJ/bamtools,pezmaster31/bamtools,pezmaster31/bamtools,kdmurray91/bamtools,SANBI-SA/bamtools,boratonAJ/bamtools,pezmaster31/bamtools,sksaskrobinsons/code,pezmaster31/bamtools,iontorrent/bamtools,SANBI-SA/bamtools,domibel/bamtools,iontorrent/bamtools