CLI sort: comment on why we don't use a mapper
CLI sort: comment on why we don't use a mapper

tkrishp/Hadoop-BAM,fnothaft/Hadoop-BAM,ryan-williams/Hadoop-BAM,HadoopGenomics/Hadoop-BAM,HadoopGenomics/Hadoop-BAM,fnothaft/Hadoop-BAM,cmnbroad/Hadoop-BAM,cmnbroad/Hadoop-BAM,HadoopGenomics/Hadoop-BAM,tomwhite/Hadoop-BAM,fnothaft/Hadoop-BAM,ryan-williams/Hadoop-BAM