Merge pull request apache#1515 from rupeshs/patch-1

Update readme

Merge pull request apache#1481 from piiswrong/master

fix cudnn layers destruction

Merge pull request apache#1390 from hjk41/master

enable setting return type for operators in registry

Merge pull request apache#1318 from rfarouni/master

Running Adam optimizer error

Merge pull request apache#1167 from jmschrei/python_metrics

ENH python metrics added, fixed

Merge pull request apache#1171 from Lodewic/patch-1

[R] Update build.md for GPU-based R pkg

Merge pull request apache#1086 from thirdwing/master

[R] misc updates: README and comments for ndsb2

Merge pull request apache#455 from tqchen/master

Fix Warning