Add ribbon/zuul features and docs plus a sample

spring-cloud-sleuth-samples/spring-cloud-sleuth-sample-messaging/src/main/java/sample/SampleMessagingApplication.java

@@ -72,7 +72,7 @@ public class SampleMessagingApplication {
 
 	// Use this for debugging (or if there is no Zipkin collector running on port 9410)
 	@Bean
-	@ConditionalOnProperty("span.logging.enabled")
+	@ConditionalOnProperty(value="sample.zipkin.enabled", havingValue="false")
 	public SpanCollector spanCollector() {
 		return new LoggingSpanCollectorImpl();
 	}

spring-cloud-sleuth-samples/spring-cloud-sleuth-sample-messaging/src/main/resources/application.yml

@@ -13,6 +13,6 @@ logging:
   pattern:
     console: '%clr(%d{yyyy-MM-dd HH:mm:ss.SSS}){faint} %clr(%5p) %clr(${PID:- }){magenta} %clr(---){faint} %clr([trace=%X{X-Trace-Id:-},span=%X{X-Span-Id:-}]){yellow} %clr([%15.15t]){faint} %clr(%-40.40logger{39}){cyan} %clr(:){faint} %m%n%wex'
 
-span:
-  logging:
-#   enabled: true
+sample:
+  zipkin:
+#   enabled: false