Added support for Feign + OkHttpClient + Sleuth

without this change we get exceptions related to not being able to extend a final class
with this change we're not wrapping any final types and we have a custom bean post processor for okhttp

fixes #513

spring-cloud-sleuth-core/pom.xml

@@ -95,6 +95,11 @@
 			<artifactId>httpclient</artifactId>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>io.github.openfeign</groupId>
+			<artifactId>feign-okhttp</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>org.aspectj</groupId>
 			<artifactId>aspectjrt</artifactId>