Update examples/imagenet/README.md
Update examples/imagenet/README.md

Co-Authored-By: takagi <bf9e8c96657b7b242831c2b7b7c309e563359b6b@gmail.com>
chainer/chainer,chainer/chainer,pfnet/chainer,niboshi/chainer,hvy/chainer,hvy/chainer,chainer/chainer,hvy/chainer,wkentaro/chainer,keisuke-umezawa/chainer,niboshi/chainer,keisuke-umezawa/chainer,niboshi/chainer,hvy/chainer,okuta/chainer,wkentaro/chainer,niboshi/chainer,okuta/chainer,keisuke-umezawa/chainer,chainer/chainer,wkentaro/chainer,tkerola/chainer,keisuke-umezawa/chainer,okuta/chainer,wkentaro/chainer,okuta/chainer