Merge branch 'master' into change-to-microbenchmarking

.gitmodules

BUILD

CMakeLists.txt

INSTALL.md

Makefile

PYTHON-MANIFEST.in

README.md

Rakefile

WORKSPACE

binding.gyp

build.yaml

config.m4

doc/combiner-explainer.md

doc/core/grpc-error.md

doc/environment_variables.md

doc/http2-interop-test-descriptions.md

examples/node/static_codegen/README.md

gRPC-Core.podspec

gRPC-ProtoRPC.podspec

gRPC-RxLibrary.podspec