Update resnet README with new checkpoints and SavedModels (#5440)
Update resnet README with new checkpoints and SavedModels (#5440)

* Update resnet README with new checkpoints and SavedModels

* add more detail on channels_first vs channels_last

* fix typo

* add disclaimer about checkpoints

tombstone/models,cshallue/models,cshallue/models,derekjchow/models,derekjchow/models,derekjchow/models,cshallue/models,tombstone/models,alexgorban/models,cshallue/models,cshallue/models,derekjchow/models,alexgorban/models,tombstone/models,derekjchow/models,tombstone/models,alexgorban/models,alexgorban/models,alexgorban/models,tombstone/models,tombstone/models