[#106] Converted UUID to Long

- Changed Random instantiation to a shared Random
- Changed the name of the converter
- Changed generator into random
- Span id is now non-nullable.
    - it gets generated in the http filter if it's not there
    - it's generated in the spring-integration channels if it wasn't set

spring-cloud-sleuth-samples/spring-cloud-sleuth-sample-ribbon/src/main/java/sample/SampleController.java

@@ -16,15 +16,14 @@
 
 package sample;
 
-import java.util.Random;
-
 import lombok.SneakyThrows;
-
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.web.bind.annotation.RequestMapping;
 import org.springframework.web.bind.annotation.RestController;
 import org.springframework.web.client.RestTemplate;
 
+import java.util.Random;
+
 /**
  * @author Spencer Gibb
  * @author Dave Syer
@@ -34,11 +33,12 @@ public class SampleController  {
 
 	@Autowired
 	private RestTemplate restTemplate;
+	@Autowired
+	private Random random;
 
 	@SneakyThrows
 	@RequestMapping("/")
 	public String hi() {
-		final Random random = new Random();
 		Thread.sleep(random.nextInt(1000));
 		String s = this.restTemplate.getForObject("http://zipkin/hi2", String.class);
 		return "hi/" + s;