Updated project to use JavaSE 11

pom.xml

@@ -1,5 +1,6 @@
 <project xmlns="http://maven.apache.org/POM/4.0.0" 
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+
   <modelVersion>4.0.0</modelVersion>
   <groupId>de.hsrm.compiler</groupId>
   <artifactId>klang</artifactId>
@@ -7,11 +8,13 @@
   <packaging>jar</packaging>
   <name>klang</name>
   <url>http://maven.apache.org</url>
+
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <antlr4.visitor>true</antlr4.visitor>
     <antlr4.listener>false</antlr4.listener>
   </properties>
+
   <dependencies>
     <dependency>
       <groupId>org.antlr</groupId>
@@ -19,16 +22,16 @@
       <version>4.5</version>
     </dependency>
   </dependencies>
+
   <build>
     <plugins>
       <!-- This plugin sets up maven to use Java 7 -->
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
-        <version>3.1</version>
+        <version>3.8.0</version>
         <configuration>
-          <source>1.7</source>
-          <target>1.7</target>
+          <release>11</release>
         </configuration>
       </plugin>
       <!-- Plugin to compile the g4 files ahead of the java files