Update to modern pytorch and fix model ckpt link

[Dawars]

I fixed up the code to make inference possible out of the box

Inference example:

from nima.inference.inference_model import InferenceModel

model = InferenceModel(path_to_model=Path('./pretrain-model.pth'))

result = model.predict_from_pil_image(img)

[shineYuSong]

where can i download the pretrained-model