Request for train.py for YOLO

[Timeless-Aim]

This is not an issue 'per se', but a request to add train.py for YOLO models or at least for YOLOv3. Chanercv framework is great, but without knowing the internals it is not so obvious how to writer train.py for YOLO. Even though chanercv generalizes many things, train.py for Fast RCNN is different than for SSD, so it might be different for YOLO. Thank you.