Patch download speed and dependency issue

Changes

• Speed up lightly-download using multithreading
• Documentation updates
• Hotfix: Fix compatability issues with pytorch-lightning>=1.7

Models

• Barlow Twins: Self-Supervised Learning via Redundancy Reduction, 2021
• Bootstrap your own latent: A new approach to self-supervised Learning, 2020
• DCL: Decoupled Contrastive Learning, 2021
• DINO: Emerging Properties in Self-Supervised Vision Transformers, 2021
• MAE: Masked Autoencoders Are Scalable Vision Learners, 2021
• MoCo: Momentum Contrast for Unsupervised Visual Representation Learning, 2019
• NNCLR: Nearest-Neighbor Contrastive Learning of Visual Representations, 2021
• SimCLR: A Simple Framework for Contrastive Learning of Visual Representations, 2020
• SimSiam: Exploring Simple Siamese Representation Learning, 2020
• SwAV: Unsupervised Learning of Visual Features by Contrasting Cluster Assignments, M. Caron, 2020