title: Tensorflow apply op to each element of a 2d tensor
body: <p>What I'm after is the ability to apply a tensorflow op to each element of a 2d tensor e.g.</p>
  
  <pre><code>input = tf.Variable([[1.0, 2.0], [3.0, 4.0])
  myCustomOp = ... # some kind of custom op that operates on 1D tensors
  finalResult = tf.[thing I'm after](input, myCustomOp)
  # when run final result should look like: [myCustomOp([1.0, 2.0]), myCustomOp([3.0, 4.0)]
  </code></pre>
  
  <p>Any ideas?</p>