Misaligns Zipkin v1 from sharing the same version number as v2 (#760)

This does two things: ensures samples don't use Zipkin v1 in any way,
and misaligns the version numbers of zipkin v1 and zipkin v2 apis.

This is an attempt to walk around the gradle plugin issue, which only
exists when someone is using both versions of zipkin.

See https://github.com/spring-projects/spring-boot/issues/10778

spring-cloud-sleuth-samples/spring-cloud-sleuth-sample-feign/src/main/java/sample/SampleFeignApplication.java

@@ -22,10 +22,10 @@ import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.cloud.netflix.feign.EnableFeignClients;
-import org.springframework.cloud.sleuth.zipkin.ZipkinSpanReporter;
 import org.springframework.context.annotation.Bean;
 
-import zipkin.Span;
+import zipkin2.Span;
+import zipkin2.reporter.Reporter;
 
 /**
  * @author Spencer Gibb
@@ -43,8 +43,8 @@ public class SampleFeignApplication {
 	// Use this for debugging (or if there is no Zipkin server running on port 9411)
 	@Bean
 	@ConditionalOnProperty(value = "sample.zipkin.enabled", havingValue = "false")
-	public ZipkinSpanReporter spanCollector() {
-		return new ZipkinSpanReporter() {
+	public Reporter<Span> spanReporter() {
+		return new Reporter<Span>() {
 			@Override
 			public void report(Span span) {
 				logger.info(span);