Merge branch 'master' of https://github.com/grpc/grpc into zookeeper

Makefile

README.md

include/grpc++/server_context.h

include/grpc/grpc.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/server_chttp2.c

src/cpp/client/channel.cc

src/cpp/client/channel.h

src/cpp/client/create_channel.cc

src/cpp/client/insecure_credentials.cc

src/cpp/client/secure_credentials.cc

src/cpp/server/insecure_server_credentials.cc

src/cpp/server/server_context.cc

src/csharp/Grpc.Auth/OAuth2Interceptors.cs

src/csharp/Grpc.Core.Tests/ChannelTest.cs

src/csharp/Grpc.Core.Tests/ClientServerTest.cs