Refactoring for sampler and assigner
Remove redundant module names in `__all__`
repeat dataset
Allow mask visualization
Update readme
Release ResNet-101 model weights for all detectors
support training on dataset with multiple ann_files
Update gpu_nms.pyx
Fix bug for gpu_nms.
Add SingleStageDetector and RetinaNet
Add support for soft-nms and potential new nms methods
update readme
