add SleuthTracer that uses lower level brave classes

to enable it, set `spring.cloud.sleuth.zipkin.braveTracer.enabled=false`

spring-cloud-sleuth-sample/pom.xml

@@ -56,6 +56,10 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-aop</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-actuator</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.projectlombok</groupId>
 			<artifactId>lombok</artifactId>