title: Tensorflow Tensor reshape and pad with zeros
body: <p>Is there a way to reshape a tensor and pad any overflow with zeros? I know ndarray.reshape does this, but as I understand it, converting a Tensor to an ndarray would require flip-flopping between the GPU and CPU. </p>
  
  <p>Tensorflow's reshape() documentation says the TensorShapes need to have the same number of elements, so perhaps the best way would be a pad() and then reshape()?</p>
  
  <p>I'm trying to achieve:</p>
  
  <pre><code>a = tf.Tensor([[1,2],[3,4]])
  tf.reshape(a, [2,3])
  a =&gt; [[1, 2, 3],
        [4, 0 ,0]]
  </code></pre>