Merge branch 'master' into rpc_mgr

BUILD

CMakeLists.txt

Makefile

binding.gyp

build.yaml

config.m4

doc/epoll-polling-engine.md

doc/images/new_epoll_impl.png

doc/images/old_epoll_impl.png

gRPC-Core.podspec

grpc.gemspec

include/grpc/impl/codegen/grpc_types.h

package.xml

src/core/ext/census/grpc_filter.c

src/core/ext/client_config/client_channel.c

src/core/ext/client_config/method_config.c

src/core/ext/client_config/method_config.h

src/core/ext/client_config/resolver_result.h

src/core/ext/client_config/subchannel.c

src/core/ext/client_config/subchannel.h