CIFAR Dataset docs do not include an entry for CIFAR100

[jvmncs]

Seems pretty low priority, but there should probably be a note here saying that there's a Dataset class for CIFAR100 that's identical to the CIFAR10 one. Would be willing to do a quick PR if there are no objections.

[alykhantejani]

Hey @jvmancuso that'd be great - please send a PR :)