Merge pull request #153 from GoogleCloudPlatform/java7

Change Hello World compiler to Java 7.

Author: lesv

managed_vms/helloworld/pom.xml

@@ -49,8 +49,8 @@
         <version>3.3</version>
         <artifactId>maven-compiler-plugin</artifactId>
         <configuration>
-          <source>1.8</source>
-          <target>1.8</target>
+          <source>1.7</source>
+          <target>1.7</target>
         </configuration>
       </plugin>
       <plugin>