Update checkstyle plugin version and remove no longer supported checkstyle module "RedundantThrows".

Make checkstyle run outside of the maven site lifecyle use checkstyle.xml.

Enable checkstyle on travis-ci.

Author: PascalSchumacher

.travis.yml

@@ -22,7 +22,7 @@ jdk:
   - oraclejdk8
 
 script:
-  - mvn test apache-rat:check clirr:check javadoc:javadoc
+  - mvn test apache-rat:check clirr:check checkstyle:check javadoc:javadoc
 
 after_success:
   - mvn clean cobertura:cobertura coveralls:report

checkstyle.xml

@@ -36,10 +36,6 @@ limitations under the License.
     <module name="RedundantImport"/>
     <module name="UnusedImports"/>
     <module name="NeedBraces"/>
-    <module name="RedundantThrows">
-      <property name="allowUnchecked" value="true"/>
-      <property name="allowSubclasses" value="true"/>
-    </module>
     <module name="LineLength">
       <property name="max" value="160"/>
     </module>

pom.xml

@@ -261,6 +261,7 @@ file comparators, endian transformation classes, and much more.
     <commons.scmPubCheckoutDirectory>site-content</commons.scmPubCheckoutDirectory>
     <!-- Override clirr version to be able to build the site on Java 8 -->
     <commons.clirr.version>2.8</commons.clirr.version>
+    <checkstyle.plugin.version>2.17</checkstyle.plugin.version>
   </properties>
 
   <build>
@@ -312,6 +313,15 @@ file comparators, endian transformation classes, and much more.
           <tarLongFileMode>gnu</tarLongFileMode>
         </configuration>
       </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-checkstyle-plugin</artifactId>
+        <version>${checkstyle.plugin.version}</version>
+        <configuration>
+          <configLocation>${basedir}/checkstyle.xml</configLocation>
+          <enableRulesSummary>false</enableRulesSummary>
+        </configuration>
+      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-scm-publish-plugin</artifactId>
@@ -334,7 +344,7 @@ file comparators, endian transformation classes, and much more.
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-checkstyle-plugin</artifactId>
-        <version>2.12.1</version>
+        <version>${checkstyle.plugin.version}</version>
         <configuration>
           <configLocation>${basedir}/checkstyle.xml</configLocation>
           <enableRulesSummary>false</enableRulesSummary>