message: Add version note to lite/python_api page.
diff: This page provides examples on how to use the TensorFlow Lite Converter and the
  TensorFlow Lite interpreter using the Python API.
  +Note: TFLite recently moved from `tf.contrib.lite` to `tf.lite`. If you are
  +using tensorflow `r1.12` or earlier you will need to add `.contrib` to the
  +commands below. `tf.lite` works with newer builds, like the nightly build,
  +which can be installed with: `pip install tf-nightly`
  +
  [TOC]
  