updated RankBoostLoss to faster method with only two matrices, rewritten update for matrixLossFunction
updated RankBoostLoss to faster method with only two matrices, rewritten update for matrixLossFunction

zhmz90/hep_ml,chrinide/hep_ml,anaderi/hep_ml,nickcdryan/hep_ml,iamfullofspam/hep_ml,iamfullofspam/hep_ml,nickcdryan/hep_ml,anaderi/hep_ml,zhmz90/hep_ml