Add basic version of cuda implementation
Add basic version of cuda implementation

chainer/chainer,okuta/chainer,pfnet/chainer,okuta/chainer,wkentaro/chainer,okuta/chainer,hvy/chainer,niboshi/chainer,chainer/chainer,niboshi/chainer,chainer/chainer,okuta/chainer,chainer/chainer,wkentaro/chainer,wkentaro/chainer,hvy/chainer,hvy/chainer,niboshi/chainer,hvy/chainer,niboshi/chainer,wkentaro/chainer