Performance Enhancement

[Dongyeongkim]

img2col.py in nn/_functions/
dataloader.py in utils/data/

Because some parts of img2col use numpy not jax.numpy, and dataloader is based on python so it is quite slow

[Dongyeongkim]

#75 the onp.add.at is changed into index add so it is enhanced. signed a die

[Dongyeongkim]

Dataloader problem remained

[Dongyeongkim]

@jepetolee will solve this issue

[Dongyeongkim]

Remove the input_elements class so it will be more faster than before

[Dongyeongkim]

Encoder is slow somehow

[Dongyeongkim]

input layer has returned, that can be used as encoder