Integration of Tensorboard

[Samcro5C]

When I tried to use the fastai callback TensorBoardCallback for a TSForecaster (minimal example from Readme), I ran into a RuntimeError (RuntimeError: Exception occured in TensorBoardCallback when calling event after_epoch: Can't call numpy() on Tensor that requires grad. Use tensor.detach().numpy() instead.), so I was wondering if tsai supports tensorboard at all or if this is a bug. Thank you in advance.

[oguiza]

@Samcro5C ,
I've created an issue as I've confirmed TensorBoarcdCallback is not working as expected.