Added CLA

Since this is a Google owned open-source repo, contributors will have
to fill out a Contributor License Agreement.

Author: puf

README.md

@@ -219,4 +219,34 @@ We can now use that in our activity to allow sending a message:
 
 Et voila: a minimal, yet fully functional, chat app in about 30 lines of code. Not bad, right?
 
-## Contributing to the library
+
+## Contributor License Agreements
+
+We'd love to accept your sample apps and patches! Before we can take them, we
+have to jump a couple of legal hurdles.
+
+Please fill out either the individual or corporate Contributor License Agreement
+(CLA).
+
+  * If you are an individual writing original source code and you're sure you
+    own the intellectual property, then you'll need to sign an [individual CLA]
+    (https://developers.google.com/open-source/cla/individual).
+  * If you work for a company that wants to allow you to contribute your work,
+    then you'll need to sign a [corporate CLA]
+    (https://developers.google.com/open-source/cla/corporate).
+
+Follow either of the two links above to access the appropriate CLA and
+instructions for how to sign and return it. Once we receive it, we'll be able to
+accept your pull requests.
+
+## Contributing A Patch
+
+1. Submit an issue describing your proposed change to the repo in question.
+1. The repo owner will respond to your issue promptly.
+1. If your proposed change is accepted, and you haven't already done so, sign a
+   Contributor License Agreement (see details above).
+1. Fork the desired repo, develop and test your code changes.
+1. Ensure that your code adheres to the existing style of the library to which
+   you are contributing.
+1. Ensure that your code has an appropriate set of unit tests which all pass.
+1. Submit a pull request.