Self-supervised learning with Image GPT

Part of the code here is adapted from Andrej Karpathy's minimalistic GPT (minGPT) implementation.

Brief description of some of the code files:

• train.py: trains an iGPT model on images/frames.
• test.py: tests an iGPT model.
• generate.py: generate samples from an iGPT model.

Please see the shell scripts for usage examples. Work in progress, more details to follow.