Added readme for chat sample

examples/chat/readme.md

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+# socket.io chat, with Azure Service Bus
+
+This example is a slightly-tweaked version of the canonical socket.io chat application.
+It has been updated to use Express version 3 and the socket.io-servicebus library
+as a back-end store to allow chat to work across multiple servers.
+
+# Running the app
+
+## Set up Service Bus
+
+To run an instance of the chat app, you have to set up a service bus namespace and topic
+first.
+
+1. Create (or locate) a Service Bus namespace to use. Get the connection string for this namespace
+   either from the Windows Azure portal or by using the azure command line tools.
+
+2. Create a topic in the Service Bus namespace. Default settings for the topic will work fine.
+
+3. Create subscriptions in the Service Bus topic; each instance of the chat app will need it's own,
+   distinct subscription. Default settings for the topic will work fine.
+
+## Running the application
+
+Before you run, you'll need to run `npm install` in the chat example's directory to set up dependencies.
+
+### Command line parameters
+
+Once you have Service Bus set up, run the application. The command line looks like:
+
+```
+  node app.js <topic> <subscription> <port> <connectionString>
+```
+
+`<topic>` is the topic name, `<subscription>` is the subscription name for this instance,
+`<port>` is the port number to run on, and `<connectionString>` is the service bus connection string.
+
+### Environment variables
+
+The app will read missing command line values from environment variables (particularly useful if deploying
+to Windows Azure):
+
+<table>
+    <thead>
+        <tr>
+            <th>Variable Name</th>
+            <th>Usage</th>
+        </tr>
+    </thead>
+    <tbody>
+        <tr>
+            <td>SB_CONN</td>
+            <td>Service bus connection string</td>
+        </tr>
+        <tr>
+            <td>PORT</td>
+            <td>Port number</td>
+        </tr>
+        <tr>
+            <td>SB_CHAT_TOPIC</td>
+            <td>Topic name</td>
+        </tr>
+        <tr>
+            <td>SB_CHAT_SUBSCRIPTION</td>
+            <td>Subscription name</td>
+        </tr>
+        <tr>
+            <td>TEST_SB_CHAT</td>
+            <td>For local tests; uses socket.io-servicebus module from source tree rather than npm</td>
+        </tr>
+    </tbody>
+</table>
+
+The `TEST_SB_CHAT` environment variable is not represented on the command line. If you're making changes to the socket.io-servicebus
+module itself, turning this environment variable on (set it to any value, it just has to exist) will cause the chat app to
+require the module from the source tree directly, rather than using the one npm installed locally.
+
+# Known Issues
+
+* The setup for service bus should not require setting up subscriptions manually; this is planned for a future version.
+
+* The "presence" messages (list of who has joined the chat) is not currently working correctly across multiple nodes. This
+  is a known issue with the chat app itself; you see similar issues when using the redis store.
+
+# Places to look
+
+The most important part of this code is in app.js file. Look for the call to io.configure. This call is where we set up Service Bus as the
+store.
+
+# Need Help?
+
+Be sure to check out the Windows Azure [Developer Forums on Stack Overflow](http://go.microsoft.com/fwlink/?LinkId=234489) if you have trouble with the provided code.
+
+# Contribute Code or Provide Feedback
+
+If you would like to become an active contributor to this project please follow the instructions provided in [Windows Azure Projects Contribution Guidelines](http://windowsazure.github.com/guidelines.html).
+
+If you encounter any bugs with the library please file an issue in the [Issues](https://github.com/WindowsAzure/socket.io-servicebus/issues) section of the project.
+
+# Learn More
+
+For documentation on how to host Node.js applications on Windows Azure, please see the [Windows Azure Node.js Developer Center](http://www.windowsazure.com/en-us/develop/nodejs/).
+
+For documentation on the Azure cross platform CLI tool for Mac and Linux, please see our readme [here] (http://github.com/windowsazure/azure-sdk-tools-xplat)