message: Updated text on eager execution
diff: "\n",
  "This model takes about ~30 seconds per epoch to train on a single Tesla K80 on Colab, as of October 2018. \n",
  "\n",
  - "Eager execution can sometimes be slower than executing the equivalent graph due to overheads of interpreting Python code. By using [tf.contrib.eager.defun](https://www.tensorflow.org/api_docs/python/tf/contrib/eager/defun) to create graph functions, we get a ~20 secs/epoch performance boost (from ~50 secs/epoch down to ~30 secs/epoch). This way we get the best of both eager execution (easier for debugging) and graph mode (better performance)."
  + "Eager execution can be slower than executing the equivalent graph as it can't benefit from whole-program optimizations on the graph, and also incurs overheads of interpreting Python code. By using [tf.contrib.eager.defun](https://www.tensorflow.org/api_docs/python/tf/contrib/eager/defun) to create graph functions, we get a ~20 secs/epoch performance boost (from ~50 secs/epoch down to ~30 secs/epoch). This way we get the best of both eager execution (easier for debugging) and graph mode (better performance)."
  ]
  },
  {
  