Raviraj Joshi

There is no problem using `AtomicBoolean` to save span finished state (See https://github.com/opentracing-contrib/java-grpc/pull/36). The `Span.isFinished()` API would be a convenience, but then again access to the `finished` state would need...

> > Only exposing public interfaces, implementations are package-private. > > This is unfortunately probably backwards incompatible, and I'm not sure worth a new version. Should we back that out?...

> Repeats the features from > #39 Plus other changes to make Travis pass! > #40 Different Implementation. This implementation uses `NullStatsReporter` just like `uber-go/tally`: https://github.com/uber-go/tally/blob/master/scope.go#L32