fix some bugs

[Topology1225]

close #43

Hi.
I had some problems running test.py and I fixed them.

• Error in pip install -r requirements.txt

ERROR: Could not find a version that satisfies the requirement torch==1.7.0 (from versions: 0.1.2, 0.1.2.post1, 0.1.2.post2, 1.7.1, 1.8.0, 1.8.1, 1.9.0)
ERROR: No matching distribution found for torch==1.7.0

• Error in python test.py --data data/coco.yaml --img 1280 --batch 32 --conf 0.001 --iou 0.65 --device 0 --cfg cfg/yolor_p6.cfg --weights yolor_p6.pt --name yolor_p6_val

Traceback (most recent call last):
  File "/home/satoharu/yolor/test.py", line 319, in <module>
    test(opt.data,
  File "/home/satoharu/yolor/test.py", line 226, in test
    plot_images(img, output_to_target(output, width, height), paths, f, names)  # predictions
  File "/home/satoharu/yolor/utils/plots.py", line 106, in output_to_target
    return np.array(targets)
  File "/home/satoharu/.pyenv/versions/3.9.6_yolor/lib/python3.9/site-packages/torch/_tensor.py", line 643, in __array__
    return self.numpy()
TypeError: can't convert cuda:0 device type tensor to numpy. Use Tensor.cpu() to copy the tensor to host memory first.

and

ERROR: pycocotools unable to run: 'numpy.float64' object cannot be interpreted as an integer
Results saved to runs/test/yolor_p6_val11

I updated your requirements.txt and utils/plots.py. Would you please check them and merge this pull request?

Thanks.

[danielcrane]

If this could be merged (and the same changes applied to the paper branch) it'd be a huge help.