Add F.cumprod
Add F.cumprod

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