Link 1.10 release notes to Bigtable doc for discoverability

PiperOrigin-RevId: 208481668

RELEASE.md

@@ -3,7 +3,7 @@
 ## Major Features And Improvements
 
 * The `tf.lite` runtime now supports `complex64`.
-* Initial Bigtable integration for `tf.data`.
+* Initial [Google Cloud Bigtable integration](https://github.com/tensorflow/tensorflow/tree/r1.10/tensorflow/contrib/bigtable) for `tf.data`.
 * Improved local run behavior in `tf.estimator.train_and_evaluate` which does not reload checkpoints for evaluation.
 * `RunConfig` now sets device_filters to restrict how workers and PS can communicate. This can speed up training and ensure clean shutdowns in some situations. But if you have jobs that require communication between workers, you will have to set custom session_options in your `RunConfig`.
 * Moved Distributions and Bijectors from `tf.contrib.distributions` to [Tensorflow Probability (TFP)](https://github.com/tensorflow/probability). `tf.contrib.distributions` is now deprecated and will be removed by the end of 2018.