Supply GBM response name in log

Also fix GBMTest
Merge branch 'master' of github.com:0xdata/h2o
Comment about the lock-down on what 'cols' means
Merge branch 'master' of github.com:0xdata/h2o
Better comment
bugfix for build.sh
Merge branch 'master' of github.com:0xdata/h2o