Change contributing.md for new contribution policy.

Change: 110504506

CONTRIBUTING.md

@@ -15,14 +15,15 @@ Follow either of the two links above to access the appropriate CLA and instructi
 
 ***NOTE***: Only original source code from you and other people that have signed the CLA can be accepted into the main repository.
 
-## Contributing code
-
-We currently use Gerrit to host and handle code changes to TensorFlow.  The main
-site is
-[https://tensorflow-review.googlesource.com/](https://tensorflow-review.googlesource.com/).
-See Gerrit [docs](https://gerrit-review.googlesource.com/Documentation/) for
-information on how Gerrit's code review system works.
-
-We are currently working on improving our external acceptance process, so
-please be patient with us as we work out the details.
-
+### Contributing code
+
+If you have improvements to TensorFlow, send us your pull requests! For those
+just getting started, Github has a [howto](https://help.github.com/articles/using-pull-requests/).
+
+If you want to contribute but you're not sure where to start, take a look at the
+[issues with the "contributions welcome" label](https://github.com/tensorflow/tensorflow/labels/contributions%20welcome).
+These are issues that we believe are particularly well suited for outside
+contributions, often because we probably won't get to them right now. If you
+decide to start on an issue, leave a comment so that other people know that
+you're working on it. If you want to help out, but not alone, use the issue
+comment thread to coordinate.