Merge branch 'master' into node_fix_message_echo

src/node/examples/math.proto

src/node/examples/route_guide.proto

src/node/examples/stock.proto

src/node/interop/empty.proto

src/node/interop/messages.proto

src/node/interop/test.proto

src/node/package.json

src/node/test/test_service.proto

src/python/README.md

src/ruby/bin/math_server.rb

src/ruby/lib/grpc/core/time_consts.rb

src/ruby/lib/grpc/generic/rpc_server.rb

tools/gce_setup/cloud_prod_test.sh

tools/gce_setup/grpc_docker.sh

tools/gce_setup/interop_test.sh