Add object tracker to YOLOv4 Darknet

Original repos:
YOLOv4: https://github.com/AlexeyAB/darknet
SORT: https://github.com/abewley/sort
DeepSORT: https://github.com/nwojke/deep_sort

How to use

• Download YOLOv4 weights here

• Install requirements

pip install -r requirements.txt

• Test with COCO pretrained model

# read arguments description for using your model and change settings
# test using coco pretrained model
python darknet_tracker.py --input track.mp4