sort fragments by vpos instead of by beg
sort fragments by vpos instead of by beg

lh3/samtools,lh3/samtools,AngieHinrichs/samtabix,AngieHinrichs/samtabix,AngieHinrichs/samtabix,lh3/samtools,AngieHinrichs/samtabix,AngieHinrichs/samtabix