implemented sync.WaitGroup to count messages in flight; changed configuration.Done to configuration.Wait(); updated examples; added optional message tracing
added config.Trace = true to examples; actor has an 'infinite' receive buffer
added queue trace statements
remove some fmt.Println from examples/request_reply.go; comments maintenance
added delay to reporting behavior completion to reduce the chances of killing running actors
Merge branch 'implement-wait-group'