Auto merge of #13 - ehiggs:fix-sigmoid-grad-dx-arg, r=MichaelHirn
Auto merge of #13 - ehiggs:fix-sigmoid-grad-dx-arg, r=MichaelHirn

fix/native: Fix sigmoid_grad to use x_diff instead of x for dx

This was a lame mistake on my part. Sorry!

autumnai/collenchyma-nn,DiamondLovesYou/collenchyma-nn,DiamondLovesYou/collenchyma-nn,autumnai/collenchyma-nn