Impement new Lambda rank interface
Download data set from web site
small change
use ndcg@all in lambdarank for ndcg
fix small bug
Merge branch 'dev' of https://github.com/tqchen/xgboost into dev

Conflicts:
	demo/rank/mq2008.conf
	demo/rank/runexp.sh
	regrank/xgboost_regrank_obj.h