improved docs, and clarified implementation
improved docs, and clarified implementation

macarthur-lab/xbrowse,macarthur-lab/xbrowse,macarthur-lab/seqr,macarthur-lab/seqr,ssadedin/seqr,macarthur-lab/xbrowse,ssadedin/seqr,macarthur-lab/xbrowse,ssadedin/seqr,ssadedin/seqr,macarthur-lab/xbrowse,macarthur-lab/xbrowse,macarthur-lab/seqr,macarthur-lab/seqr,macarthur-lab/seqr,ssadedin/seqr