add vgg19 to docs
add vgg19 to docs

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