message: return this in on() and off() methods in changes observable
diff: @@ -45,12 +45,14 @@ export class ChangesObservable<T, TConnectionState extends IChangesConnectionSta
  this._errorSubscribers.add(handler as (error: Error) => void);
  break;
  }
  +
  + return this;
  }
  public removeListener(event: "data", handler: (value: T) => void);
  public removeListener(event: "error", handler: (error: Error) => void);
  public removeListener(event: "data" | "error", handler: ((value: T) => void) | ((error: Error) => void)) {
  - this.off(event as any, handler as any);
  + return this.off(event as any, handler as any);
  }
  public off(event: "data", handler: (value: T) => void);
  @@ -77,6 +79,8 @@ export class ChangesObservable<T, TConnectionState extends IChangesConnectionSta
  }
  break;
  }
  +
  + return this;
  }
  public send(msg: T): void {
  