Merge branch 'master' of github.com:google/grpc into go-auth-tests

Makefile

build.json

include/grpc++/credentials.h

include/grpc/grpc_security.h

src/core/httpcli/httpcli.c

src/core/json/json.c

src/core/json/json_reader.c

src/core/json/json_writer.c

src/core/security/auth.c

src/core/security/credentials.c

src/core/security/credentials.h

src/core/security/credentials_posix.c

src/core/security/credentials_win32.c

src/core/security/google_default_credentials.c

src/core/security/security_context.c

src/cpp/client/credentials.cc

src/node/examples/pubsub/empty.proto

src/node/examples/pubsub/label.proto

src/node/examples/pubsub/pubsub.proto

src/node/examples/pubsub/pubsub_demo.js