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

BUILD

CMakeLists.txt

Makefile

binding.gyp

build.yaml

config.m4

doc/PROTOCOL-HTTP2.md

doc/environment_variables.md

gRPC-Core.podspec

grpc.def

grpc.gemspec

include/grpc++/impl/codegen/call.h

include/grpc++/impl/codegen/config.h

include/grpc/impl/codegen/grpc_types.h

include/grpc/impl/codegen/slice.h

include/grpc/slice_buffer.h

package.xml

src/boringssl/err_data.c

src/compiler/cpp_generator.cc

src/core/ext/client_channel/client_channel.c