Merge branch 'master' into fc_1dstream

.gitmodules

BUILD

CMakeLists.txt

Makefile

README.md

binding.gyp

build.yaml

composer.json

config.m4

doc/PROTOCOL-HTTP2.md

doc/core/pending_api_cleanups.md

doc/cpp/pending_api_cleanups.md

doc/environment_variables.md

doc/interop-test-descriptions.md

etc/roots.pem

examples/node/static_codegen/greeter_client.js

examples/php/composer.json

examples/ruby/route_guide/route_guide_client.rb

examples/ruby/route_guide/route_guide_server.rb

gRPC-Core.podspec