* checkpoint
* Pass context through ServeDNS, enable gRPC tracing
* Fix types and make tracer available to proxy. go fmt
* Fix imports
* Use the DoNotStartTrace option
* Change to SpanFilter from DoNotStartTrace
* Use new name (IncludeSpan)
* Final names
* Add tests; fix possible client/conn leaks in grpc
* go fmt
* WIP: Client-side of gRPC proxy
* Add tests
* gofmt
* Implement OnShutdown; add a little logging
* Update for context in Exchange change
* go fmt
* Update README
* Review comments
* Compiling is good
* More README improvements