CNVkit: better lower boundary for antitarget
CNVkit: better lower boundary for antitarget

Thanks to @etal: https://github.com/chapmanb/bcbio-nextgen/commit/44e8685e7ec9bd69bc0c7aa9ac9967a224a66f22#commitcomment-20376889

vladsaveliev/bcbio-nextgen,chapmanb/bcbio-nextgen,brainstorm/bcbio-nextgen,chapmanb/bcbio-nextgen,vladsaveliev/bcbio-nextgen,chapmanb/bcbio-nextgen,biocyberman/bcbio-nextgen,brainstorm/bcbio-nextgen,a113n/bcbio-nextgen,lbeltrame/bcbio-nextgen,lbeltrame/bcbio-nextgen,vladsaveliev/bcbio-nextgen,brainstorm/bcbio-nextgen,a113n/bcbio-nextgen,biocyberman/bcbio-nextgen,a113n/bcbio-nextgen,lbeltrame/bcbio-nextgen,biocyberman/bcbio-nextgen