Merge github.com:grpc/grpc into write_buffering

BUILD

CMakeLists.txt

Makefile

README.md

binding.gyp

build.yaml

config.m4

doc/cpp/perf_notes.md

doc/interop-test-descriptions.md

doc/negative-http2-interop-test-descriptions.md

gRPC-Core.podspec

grpc.gemspec

include/grpc++/grpc++.h

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

include/grpc/impl/codegen/port_platform.h

include/grpc/support/log_windows.h

package.json

package.xml

src/core/ext/README.md

src/core/ext/census/tracing.c