Implement remainder of Spring Boot Checkstyle code rules

Fixes #532

Implements most of the remaining rules from Spring Boot, except JavaDoc + a few additional ones

spring-cloud-stream-rxjava/src/main/java/org/springframework/cloud/stream/annotation/rxjava/RxJavaProcessorConfiguration.java

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package org.springframework.cloud.stream.annotation.rxjava;
 
 import org.springframework.beans.factory.annotation.Autowired;

spring-cloud-stream-rxjava/src/main/java/org/springframework/cloud/stream/annotation/rxjava/SubjectMessageHandler.java

@@ -73,7 +73,7 @@ public class SubjectMessageHandler extends AbstractMessageProducingHandler imple
 
 	private volatile Subscription subscription;
 
-	private volatile boolean running = false;
+	private volatile boolean running;
 
 	@SuppressWarnings({"unchecked", "rawtypes"})
 	public SubjectMessageHandler(RxJavaProcessor processor) {