add link to numpy.matmul function
add link to numpy.matmul function

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