Merge pull request apache#1680 from thirdwing/master

[R] added a verbose option to `mx.mlp` in R package. close apache#1608

Merge pull request apache#1580 from linmx0130/master

add AdaGrad optimizer in python, a revised version

Merge pull request apache#1544 from hjk41/master

include stdint.h in c_api.h since uint64_t is not defined

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