Java 8 compiler settings fix

Former-commit-id: dac9d0e0

pom.xml

@@ -159,6 +159,15 @@
                 </configuration>
             </plugin>
 
+            <plugin>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>2.3.2</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+
             <!-- Signing -->
             <!--plugin>
                 <groupId>org.apache.maven.plugins</groupId>