v0.5.1

What's Changed

• Fix bug 1 : MetricsCallback and run_pl_training

• on_train_batch_end hook doesnt require dataloader_idx now.
• FitLoop object of pytorch-lightning doesnt have public property should_accumulate since version 1.5.0
• run_pl_training: pytorch-lightning changes the initialization method of Trainer, especially for multi-gpu training.