Haiku 0.0.2

Changelog:

• Changed the default value of apply_rng to True in hk.transform to simplify the apply_fn signature.
• Made ConvND, ConvNDTranspose, ResetCore and pooling modules optionally batched.
• Added hk.GroupNorm.
• Added hk.scan.
• Changed hk.BatchNorm to always create state for moving averages.
• Changed use_projection in hk.nets.ResNet to take a sequence of bools.
• Exposed hk.net.ResNet.{BlockGroup, BlockV1, BlockV2}.
• Added original_dtype to ParamContext to expose the original parameter dtype to custom_getters.
• Added GAN example notebook.