updated readme with usage information

hystrix/README.md

@@ -1 +1,26 @@
-This project is a sample of using just the hystrix starter
+# About
+This project is a sample of using just the Hystrix Starter.  For more information see the
+[Hystrix documentation](http://cloud.spring.io/spring-cloud-static/spring-cloud.html#_circuit_breaker_hystrix_clients).
+
+# Usage
+This simple app contains two endpoints both surrounded by Hystrix circuit breakers.
+See [HystrixApplication.java](https://github.com/spring-cloud-samples/tests/blob/master/hystrix/src/main/java/demo/HystrixApplication.java) for
+the endpoint definitions.
+
+## /ok
+The `/ok` endpoint just returns the String 'OK' and should actually never trip the circuit breaker since there is no
+way for it to "fail".
+
+## /fail
+The `/fail` endpoint will throw a `RuntimeException` unless the header `X-NO-FAIL` is present.  If you hit the
+`/fail` endpoint fast enough, the circuit will open and Hystrix will return the response from the fallback method
+defined in [MyService.java](https://github.com/spring-cloud-samples/tests/blob/master/hystrix/src/main/java/demo/MyService.java#L28).
+Once the circuit is open you will see the `/fail` endpoint return the string `from the fallback`.  The circuit will remain
+open until a successful request is made to the fail endpoint.  This is where the `X-NO-FAIL` header comes in handy.  If
+the header is present in the request made to `/fail`, the `RuntimeException` will not be thrown.  If you do this enough
+while the circuit is open than the circuit will eventually close.
+
+## Using The Hystrix Dashboard
+You can use the [Hystrix Dashboard](https://github.com/spring-cloud-samples/hystrix-dashboard) sample to visualize
+the state of the circuit breakers in this application.  To do this, follow the instructions in the README for the
+Hystrix Dashboard sample to start the dashboard and then point it at 'http://localhost:8080/hystrix.stream'.