Update readme to reflect end of active dev on service SDK (#1284)

iothub_service_client/readme.md

@@ -1,6 +1,19 @@
 # Microsoft Azure IoT service SDK for C
 
+## End of active development for service SDK
+
+The Azure IoT Service SDK for C is no longer under active development.
+
+We will continue to fix critical bugs such as crashes, data corruption, and security vulnerabilities.  We will **NOT** add any new feature or fix bugs that are not critical, however.
+
+Azure IoT Service SDK support is available in higher-level languages ([C#](https://github.com/Azure/azure-iot-sdk-csharp), [Java](https://github.com/Azure/azure-iot-sdk-java), [Node](https://github.com/Azure/azure-iot-sdk-node), [Python](https://github.com/Azure/azure-iot-sdk-python)).
+
+The rest of this repo - for instance the [device sdk](../iothub_client_device) for deploying code to devices - continues to be under active development.  This ending of new features only applies to code under this subfolder.
+
+## Folder Layout
+
 This folder contains the following 
+
 * The Azure IoT service SDK for C to easily and securely manage an instance of the Microsoft Azure IoT Hub service as well as send Cloud to Device messages through IOT Hub.
 * Samples showing how to use the SDK
 
@@ -21,6 +34,5 @@ Instructions on how to setup your development environemnt can be found [here][de
 The repository contains a set of simple samples that will help you get started.
 You can find a list of these samples with instructions on how to run them [here][samples]. 
 
-
 [devbox_setup]: ../doc/devbox_setup.md
 [samples]: ./samples/