Add the `$upstream_status` value to the log line (#11)

# `nginx-sidecar` changelog

## 0.3.4

- Add `$upstream_status` to the nginx access log line

## 0.3.3

- Add `--fail` to the curl health check. This causes curl to return non-zero exit codes

0.3.3

0.3.4

  default_type application/octet-stream;

  log_format  main  '[nginx] method=$request_method path=$request_uri '

                    'status=$status duration=$request_time size=$body_bytes_sent '

                    'status=$status upstream_status=$upstream_status duration=$request_time size=$body_bytes_sent '

                    '"$remote_user" "$http_referer" "$http_user_agent"';

  # Log to stdout.