added convenience comparator wrapper
added convenience comparator wrapper

BohuTANG/ft-index,BohuTANG/ft-index,ottok/PerconaFT,percona/PerconaFT,ottok/PerconaFT,BohuTANG/ft-index,kuszmaul/PerconaFT-tmp,percona/PerconaFT,kuszmaul/PerconaFT-tmp,ottok/PerconaFT,percona/PerconaFT,ottok/PerconaFT,kuszmaul/PerconaFT,BohuTANG/ft-index,kuszmaul/PerconaFT,kuszmaul/PerconaFT,kuszmaul/PerconaFT-tmp,percona/PerconaFT,kuszmaul/PerconaFT,kuszmaul/PerconaFT-tmp