Detailed fold structure.

[freshn]

@yuanyuanli85 Hello. Could you please list a more detailed file structure of the 'data' fold otherwise it is hard to know the corresponding file using in test.py and demo.py. For instance, I am confused about which file is coresponding to 'val_split.cls'. Another example is that in './data/train' fold, does it contain both images from 'train1' and 'train2' from the original data or not? Thank you.