title: Using tf.tile to replicate a tensor N times
body: <p>My current tensor has shape of (3, 2), e.g.,</p>
  
  <p><code>[[ 1.  2.]
   [ 2.  1.]
   [-2. -1.]]</code></p>
  
  <p>I would like to expand to a shape of (1, 3, 2) with each second dimension a replica of the entire tensor, e.g.,</p>
  
  <pre><code>[[[ 1.  2.]
    [ 2.  1.]
    [ -2.  -1.]]
   [[ 1.  2.]
    [ 2.  1.]
    [ -2.  -1.]]
  [[ 1.  2.]
    [ 2.  1.]
    [ -2. -1.]]]
  </code></pre>
  
  <p>I tried the folllowing code but it only replicate each row instead.</p>
  
  <pre><code>tiled_vecs = tf.tile(tf.expand_dims(input_vecs, 1), [1, 3, 1])
  </code></pre>
  
  <p>Results in</p>
  
  <pre><code>[[[ 1.  2.]
  [ 1.  2.]
  [ 1.  2.]]
  [[ 2.  1.]
   [ 2.  1.]
   [ 2.  1.]]
  [[-2. -1.]
   [-2. -1.]
   [-2. -1.]]]
  </code></pre>