Add tests for Chain.copy
Add tests for Chain.copy

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