Added channel pruning on a pytorch version of YOLOv3
Use original darknet cfg and weights file as input.
It will generate pruned_cfg and pruned_weights which could be used with the original darknet.
Also compatible with AlexeyAB darknet modification.

There is already a pruned model of YOLOv3-TINY trained on VOC2007+VOC2012 in the output folder.
Check out the pruned filters in the pruned_channels.txt