Planned updates

• Upgrade to pytorch-1.0
• Allow support for models to have custom loss functions.
• Pretrained models on S3 for common models-dataset pairs
• Compatibility matrix for dataset with models
• RefineNet and E-Net implementations
• MS-COCO, Mapillary Vistas and BDD-100k datasets
• Interface to combine datasets with a user-given mapping dictionary
• Improved metric logging