Merge branch 'master' of github.com:grpc/grpc into the-ultimate-showdown

doc/connectivity-semantics-and-api.md

include/grpc++/client_context.h

include/grpc/census.h

src/core/security/client_auth_filter.c

src/cpp/client/channel.cc

src/cpp/client/client_context.cc

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

src/csharp/Grpc.Core.Tests/Grpc.Core.Tests.csproj

src/csharp/Grpc.Core/ClientBase.cs

src/objective-c/GRPCClient/GRPCCall+OAuth2.m

src/objective-c/GRPCClient/GRPCCall.h

src/objective-c/GRPCClient/GRPCCall.m

src/objective-c/tests/GRPCClientTests.m

src/ruby/ext/grpc/rb_channel.c

test/core/end2end/tests/bad_hostname.c