[Feature Request] Add Other State-of-the-art Detection Models

[ahkarami]

Hi, Do you have any plan for adding other new State-of-the-art Detection Models (i.e., RefineDet & S3FD & RFBNet)?

[zhanghang1989]

For detection models, we have FPN, Mask RCNN, YOLO V3, RetinaNet in our roadmap. @zhreshold please corrects me, if it is wrong.