text: Title: wrong histograms
  Body: Hi, I am having problems plotting histograms.  I think there is a very good chance that it is not because of a bug in tensorboard-pytorch, but I'm not sure what I could be doing wrong, and I'm not sure where to ask, so if someone could help I would appreciate it.
  
  I am trying to plot histograms of the gradients like this:
  
  ```
  loss.backward()
  for n, p in filter(lambda np: np[1].grad is not None, spectral_model.named_parameters()):
      print(n, p.grad.data.min(), p.grad.data.max())
      summary_writer.add_histogram(n, p.grad.data.cpu().numpy(), global_step=step)
  ```
  The mins and maxes show that the values are all between -.15 and .15 (and in fact most values are much closer to zero than that).  But the histograms seem to show that all the values are located at one extremely high value, like 3.01e+18:
  
  ![image](https://user-images.githubusercontent.com/8763901/31584773-71fc0df4-b1bd-11e7-9fde-8ad45eafee71.png)
  
  