Update README.md

Update README.md

Update README.md

Update README.md

Update requirements.txt

Update installation

Remove `pillow`'s version

Update

Merge remote-tracking branch 'origin/master'

Add requirements.txt

Create LICENSE

Add global variable DATASET_ROOT. It's more readable.

Finished

For training set only

Refactor `cuda()`'s parameter by `CUDA_DEVICES`