message: Add most accurate return type
diff: @@ -132,7 +132,7 @@ declare namespace botkit {
  addQuestion(message: string | M, cb: ConversationCallback<M>, capture_options: ConversationCaptureOptions, thread: string): void;
  ask(message: string | M, cb: ConversationCallback<M>, capture_options?: ConversationCaptureOptions): void;
  beforeThread(thread: string, callback: (convo: this, next: (err: string | Error) => void) => void): void;
  - collectResponse(key: string, value: string);
  + collectResponse(key: string, value: string): void;
  extractResponse(key: string): string;
  extractResponses(): { [key: string]: string };
  gotoThread(thread: string): void;
  