Fix mnist example
Fix mnist example

woodshop/complex-chainer,chainer/chainer,tkerola/chainer,chainer/chainer,okuta/chainer,hvy/chainer,ktnyt/chainer,okuta/chainer,elviswf/chainer,hvy/chainer,ktnyt/chainer,AlpacaDB/chainer,cupy/cupy,delta2323/chainer,ktnyt/chainer,cemoody/chainer,cupy/cupy,wkentaro/chainer,sinhrks/chainer,nushio3/chainer,niboshi/chainer,hidenori-t/chainer,bayerj/chainer,okuta/chainer,truongdq/chainer,sinhrks/chainer,jfsantos/chainer,kikusu/chainer,muupan/chainer,keisuke-umezawa/chainer,niboshi/chainer,hvy/chainer,ronekko/chainer,t-abe/chainer,sou81821/chainer,1986ks/chainer,minhpqn/chainer,ktnyt/chainer,ikasumi/chainer,niboshi/chainer,pfnet/chainer,Kaisuke5/chainer,tigerneil/chainer,t-abe/chainer,aonotas/chainer,chainer/chainer,nushio3/chainer,okuta/chainer,truongdq/chainer,niboshi/chainer,umitanuki/chainer,jnishi/chainer,ttakamura/chainer,jnishi/chainer,tereka114/chainer,laysakura/chainer,ytoyama/yans_chainer_hackathon,kuwa32/chainer,rezoo/chainer,jnishi/chainer,yanweifu/chainer,kashif/chainer,cupy/cupy,keisuke-umezawa/chainer,woodshop/chainer,wkentaro/chainer,cupy/cupy,muupan/chainer,kikusu/chainer,keisuke-umezawa/chainer,AlpacaDB/chainer,keisuke-umezawa/chainer,hvy/chainer,tscohen/chainer,jnishi/chainer,ttakamura/chainer,ysekky/chainer,masia02/chainer,benob/chainer,anaruse/chainer,benob/chainer,kiyukuta/chainer,chainer/chainer,wkentaro/chainer,wavelets/chainer,wkentaro/chainer