add upgrade guide
add upgrade guide

hvy/chainer,jnishi/chainer,chainer/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,ktnyt/chainer,hvy/chainer,jnishi/chainer,wkentaro/chainer,pfnet/chainer,niboshi/chainer,chainer/chainer,wkentaro/chainer,ktnyt/chainer,jnishi/chainer,chainer/chainer,okuta/chainer,okuta/chainer,hvy/chainer,ktnyt/chainer,wkentaro/chainer,niboshi/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,jnishi/chainer,ktnyt/chainer,okuta/chainer,okuta/chainer,hvy/chainer,niboshi/chainer,niboshi/chainer,wkentaro/chainer,chainer/chainer,tkerola/chainer