message: doc: update document key
diff: @@ -104,7 +104,7 @@ GET /error
  [
  {
  "method": "error",
  - "date": 1346846400,
  + "timestamp": 1346846400,
  "errType": "TypeError",
  "message": "Cannot read property 'name' of null",
  "stack": "2017-11-29 15:01:20 Error: read ECONNRESET",
  @@ -206,7 +206,7 @@ GET /trace
  [
  {
  - "date": "1511977377963",
  + "timestamp": "1511977377963",
  "appName": "DEFAULT_APP",
  "traceId": "1e084d5515118598316151001dd73d",
  "duration": 139,
  