New loader: The category loader takes an index as input and turns it into a category defined in your meta.yaml. This reduces the array size a lot, as we e.g. do not have to store a large string array but can store far better compressed integer array.
image and numpy loaders now have a root parameter, which is prepended to the path of a given example. This increases the portability of datasets and also make the sizes of the label arrays smaller.
Adds cool new features to the MetaDataset: