Fix build on JDK 11 so CI build can run (#23)

diff --git a/pom.xml b/pom.xml
index de8a4c1..059e6ae 100644
--- a/pom.xml
+++ b/pom.xml
@@ -44,8 +44,11 @@
   </issueManagement>
   <properties>
     <findbugs.maxRank>12</findbugs.maxRank>
-    <hadoop.version>2.6.3</hadoop.version>
+    <hadoop.version>2.6.5</hadoop.version>
     <logback.version>1.1.3</logback.version>
+    <maven.compiler.release>8</maven.compiler.release>
+    <maven.compiler.source>1.8</maven.compiler.source>
+    <maven.compiler.target>1.8</maven.compiler.target>
     <slf4j.version>1.7.12</slf4j.version>
     <twill.version>0.12.0</twill.version>
   </properties>
@@ -129,6 +132,10 @@
           <groupId>asm</groupId>
           <artifactId>asm</artifactId>
         </exclusion>
+        <exclusion>
+          <groupId>jdk.tools</groupId>
+          <artifactId>jdk.tools</artifactId>
+        </exclusion>
       </exclusions>
     </dependency>
     <dependency>
@@ -149,6 +156,23 @@
     </dependency>
   </dependencies>
   <build>
+    <pluginManagement>
+      <plugins>
+        <plugin>
+          <groupId>org.apache.maven.plugins</groupId>
+          <artifactId>maven-compiler-plugin</artifactId>
+          <version>3.8.1</version>
+        </plugin>
+        <plugin>
+          <groupId>org.apache.maven.plugins</groupId>
+          <artifactId>maven-javadoc-plugin</artifactId>
+          <version>3.1.1</version>
+          <configuration>
+            <doclint>all,-missing</doclint>
+          </configuration>
+        </plugin>
+      </plugins>
+    </pluginManagement>
     <plugins>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>