use new dataset classes in seq2seq example
use new dataset classes in seq2seq example

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