[s3] modified source to 1.7

pom.xml

@@ -125,8 +125,8 @@ LICENSE file.
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.3</version>
         <configuration>
-          <source>1.6</source>
-          <target>1.6</target>
+          <source>1.7</source>
+          <target>1.7</target>
         </configuration>
       </plugin>
       <plugin>