Add the ability to auto restart the last run when started after a crash (#191)

* Added autoresume after crash functionality to the trackers

* Updated documentation

* Clarified what goes in the autorestart object

* Fixed style issues

Unraveled conditional block

Chnaged to using helper function to get step count

dalle2_pytorch/trainer.py

@@ -509,7 +509,6 @@ class DecoderTrainer(nn.Module):
         self.register_buffer('steps', torch.tensor([0] * self.num_unets))
 
         decoder, *optimizers = list(self.accelerator.prepare(decoder, *optimizers))
-        schedulers = list(self.accelerator.prepare(*schedulers))
 
         self.decoder = decoder