added ZippedImageDataset and MultiZippedImageDataset
added ZippedImageDataset and MultiZippedImageDataset

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