Dataloaders and DataSamplers

DataLoader(dataset, batch_size=1, ...)      # loads data batches agnostic
                                            # of structure of individual data points
sampler.Sampler(dataset,...)                # abstract class dealing with
                                            # ways to sample from dataset
sampler.XSampler where ...                  # Sequential, Random, SubsetRandom,
                                            # WeightedRandom, Batch, Distributed