Answer major question in README.

This answers the three questions laid out in the community lead handbook:

* What should I do if I found a bug?
* What should I do if I have a question?
* What should I do if I want to contribute time to this project?

Test Plan:
Use GitHub's preview tab to ensure the Markdown is valid.

README.md

@@ -11,6 +11,10 @@ This repo consists of two parts:
 
 **Khan Exercises is no longer used for development of new exercises at Khan Academy.** We're always looking to improve the exercises that are currently built with Khan Exercises, but at this time we don't intend to add any new exercises. New exercises on Khan Academy are written by many content experts using [Perseus](https://github.com/Khan/perseus) and stored in our datastore as individual questions.
 
+The bulk of our bug reports now go into [Zen Desk](https://khanacademy.zendesk.com) where volunteers surface issues to KA developers, but we still process issues and PRs that come in through this repository. The goal is to keep high-quality bug reports and feature requests in this repository so awesome OSS developers who want to help KA have the tools do so.
+
+If you're looking to contribute time, looking through [our wiki](https://github.com/Khan/khan-exercises/wiki) is a good place to start. Questions should go into [the issue tracker](https://github.com/Khan/khan-exercises/issues) (we may set up gitter if there ends up being a high volume of questions).
+
 ## Licensing
 
 Copyright (c) 2015 Khan Academy