Add tests to check pickled & unpickled Variable
Add tests to check pickled & unpickled Variable

cupy/cupy,delta2323/chainer,hvy/chainer,cupy/cupy,tkerola/chainer,wkentaro/chainer,hvy/chainer,okuta/chainer,hvy/chainer,cupy/cupy,chainer/chainer,okuta/chainer,chainer/chainer,ysekky/chainer,wkentaro/chainer,ktnyt/chainer,kiyukuta/chainer,niboshi/chainer,keisuke-umezawa/chainer,niboshi/chainer,anaruse/chainer,niboshi/chainer,niboshi/chainer,okuta/chainer,keisuke-umezawa/chainer,kashif/chainer,jnishi/chainer,jnishi/chainer,jnishi/chainer,ronekko/chainer,ktnyt/chainer,keisuke-umezawa/chainer,wkentaro/chainer,aonotas/chainer,ktnyt/chainer,okuta/chainer,chainer/chainer,chainer/chainer,keisuke-umezawa/chainer,hvy/chainer,cupy/cupy,jnishi/chainer,pfnet/chainer,wkentaro/chainer,rezoo/chainer,ktnyt/chainer