Added OpenTracing support; fixes #599

docs/src/main/asciidoc/features.adoc

@@ -39,14 +39,14 @@ a baggage element then it will be sent downstream either via HTTP or messaging t
 
 * Provides a way to create / continue spans and add tags and logs via annotations.
 
-* Provides simple metrics of accepted / dropped spans.
-
 * If `spring-cloud-sleuth-zipkin` then the app will generate and collect Zipkin-compatible traces.
 By default it sends them via HTTP to a Zipkin server on localhost (port 9411).
 Configure the location of the service using `spring.zipkin.baseUrl`.
   - If you depend on `spring-rabbit` or `spring-kafka` your app will send traces to a broker instead of http.
   - Note: `spring-cloud-sleuth-stream` is deprecated and should no longer be used.
 
+* Spring Cloud Sleuth is http://opentracing.io/[OpenTracing] compatible
+
 IMPORTANT: If using Zipkin, configure the percentage of spans exported using `spring.sleuth.sampler.percentage`
 (default 0.1, i.e. 10%). *Otherwise you might think that Sleuth is not working cause it's omitting some spans.*
 

docs/src/main/asciidoc/spring-cloud-sleuth.adoc

@@ -931,6 +931,12 @@ on how to create a Stream Zipkin server.
 
 == Integrations
 
+=== OpenTracing
+
+Spring Cloud Sleuth is http://opentracing.io/[OpenTracing] compatible. If you have
+OpenTracing on the classpath we will automatically register the OpenTracing
+`Tracer` bean. If you wish to disable this just set `spring.sleuth.opentracing.enabled` to `false`
+
 === Runnable and Callable
 
 If you're wrapping your logic in `Runnable` or `Callable` it's enough to wrap those classes in their Sleuth representative.