Merge github.com:grpc/grpc into propagate

Makefile

README.md

include/grpc++/client_context.h

include/grpc++/server_context.h

include/grpc/grpc.h

src/compiler/generator_helpers.h

src/core/iomgr/fd_posix.c

src/core/iomgr/sockaddr_utils.c

src/core/iomgr/tcp_server_windows.c

src/core/iomgr/tcp_windows.c

src/core/surface/channel.c

src/core/surface/channel_connectivity.c

src/core/transport/chttp2/alpn.c

src/cpp/client/channel.cc

src/cpp/client/channel.h

src/cpp/client/client_context.cc

src/cpp/client/create_channel.cc

src/cpp/client/insecure_credentials.cc

src/cpp/client/secure_credentials.cc

src/cpp/server/server_context.cc