Fix build break

Author: rdasgupt

pom.xml

@@ -10,9 +10,9 @@
         <!-- source & target java version for MQTT Client -->
         <maven.compiler.source>1.8</maven.compiler.source>
         <maven.compiler.target>1.8</maven.compiler.target>
-        <!-- mqttclient.java.version>1.8</mqttclient.java.version -->
+        <mqttclient.java.version>1.8</mqttclient.java.version>
         <!-- source & target java version for others modules -->
-        <!-- java.version>1.8</java.version -->
+        <java.version>1.8</java.version>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <build.level>${maven.build.timestamp}</build.level>
         <tycho.version>1.7.0</tycho.version>
@@ -115,7 +115,7 @@
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-compiler-plugin</artifactId>
-                    <version>3.5.1</version>
+                    <version>2.7.1</version>
                     <configuration>
                         <encoding>${project.build.sourceEncoding}</encoding>
                         <source>${java.version}</source>