Update examples/pubsub/README

Update CONTRIBUTING.md

We have decided our release version number shall be 0.5.0.

Go auth tests

Massage wording and fix the instructions for run_tests to remove reference to non-existsant -l all option.

Removes a redundant canary test

Make PHP compile

Grpc ruby remove default creds canary

Fixed TLS host resolution problems

Python readme fixes

Fix read through null pointer

Improvements in gRPC C# support for Windows

Updated Python protoc plugin and Python plugin testing.

Grpc ruby switch auth to google auth library ruby

Added support for true synchronous unary call & some performance tests.