Get things shipshape for demo

[RehanSD]

Add the following models:

• ImageNet ResNet18
• ImageNet ResNet50
• ImageNet ResNet152
• Mask R-CNN for Detection
• Faster R-CNN for Detection
• Keypoint R-CNN for Detection
• HuggingFace GPT2 LM Head Model
• HuggingFace XLNet LM Head Model Add a yarn lock file (which solves the issue that sometimes crops up with fsevents being deprecated. Merge package structure of modelzoo and model_io and release modelzoov0.3.1 to pypi.