Fix Checkstyle violations

* Make version block for dependencies as code-switcher in the XML, ZeroMQ and Zookeeper docs

spring-integration-xml/src/main/java/org/springframework/integration/xml/transformer/MarshallingTransformer.java

@@ -18,7 +18,6 @@ package org.springframework.integration.xml.transformer;
 
 import java.io.IOException;
 
-import javax.xml.parsers.ParserConfigurationException;
 import javax.xml.transform.Result;
 
 import org.springframework.messaging.Message;

src/reference/asciidoc/xml.adoc

@@ -17,8 +17,8 @@ Spring Integration's XML support extends the core of Spring Integration with the
 You need to include this dependency into your project:
 
 ====
+[source, xml, subs="normal", role="primary"]
 .Maven
-[source, xml, subs="normal"]
 ----
 <dependency>
     <groupId>org.springframework.integration</groupId>
@@ -27,8 +27,8 @@ You need to include this dependency into your project:
 </dependency>
 ----
 
+[source, groovy, subs="normal", role="secondary"]
 .Gradle
-[source, groovy, subs="normal"]
 ----
 compile "org.springframework.integration:spring-integration-xml:{project-version}"
 ----

src/reference/asciidoc/zeromq.adoc

@@ -8,8 +8,8 @@ All components encapsulate ZeroMQ socket lifecycles and manage threads for them
 You need to include this dependency into your project:
 
 ====
+[source, xml, subs="normal", role="primary"]
 .Maven
-[source, xml, subs="normal"]
 ----
 <dependency>
     <groupId>org.springframework.integration</groupId>
@@ -18,8 +18,8 @@ You need to include this dependency into your project:
 </dependency>
 ----
 
+[source, groovy, subs="normal", role="secondary"]
 .Gradle
-[source, groovy, subs="normal"]
 ----
 compile "org.springframework.integration:spring-integration-zeromq:{project-version}"
 ----

src/reference/asciidoc/zookeeper.adoc

@@ -10,8 +10,8 @@ Version 4.2 added https://zookeeper.apache.org/[Zookeeper] support to the framew
 You need to include this dependency into your project:
 
 ====
+[source, xml, subs="normal", role="primary"]
 .Maven
-[source, xml, subs="normal"]
 ----
 <dependency>
     <groupId>org.springframework.integration</groupId>
@@ -20,8 +20,8 @@ You need to include this dependency into your project:
 </dependency>
 ----
 
+[source, groovy, subs="normal", role="secondary"]
 .Gradle
-[source, groovy, subs="normal"]
 ----
 compile "org.springframework.integration:spring-integration-zookeeper:{project-version}"
 ----