v0.2.2

NNlibCUDA v0.2.2

Diff since v0.2.1

Closed issues:

• Slow ∇softmax! compared with generic version. (#30)

Merged pull requests:

• track_stats option for batchnorm (#36) (@CarloLucibello)
• update softmax tests to match NNlib 0.8.3 (#44) (@mcabbott)