Merge github.com:grpc/grpc into filter-selection

CONTRIBUTING.md

Makefile

build.yaml

examples/cpp/helloworld/README.md

examples/node/package.json

examples/ruby/route_guide/route_guide_client.rb

include/grpc++/impl/codegen/completion_queue_tag.h

include/grpc++/impl/codegen/impl/async_stream.h

include/grpc++/impl/codegen/impl/status_code_enum.h

include/grpc++/impl/codegen/impl/sync.h

include/grpc++/impl/grpc_library.h

include/grpc++/impl/proto_utils.h

include/grpc++/security/auth_context.h

include/grpc++/security/auth_metadata_processor.h

include/grpc++/security/credentials.h

include/grpc++/security/server_credentials.h

include/grpc/census.h

include/grpc/compression.h

include/grpc/grpc_security.h

include/grpc/impl/codegen/propagation_bits.h