Bump java default source and target level to 7

Change-Id: Ibefd5cb16937868e737992e3ebf07ba19076654a
diff --git a/pom.xml b/pom.xml
index 31fc414..fffb832 100644
--- a/pom.xml
+++ b/pom.xml
@@ -290,8 +290,8 @@
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
         <configuration>
-          <source>1.6</source>
-          <target>1.6</target>
+          <source>1.7</source>
+          <target>1.7</target>
           <encoding>UTF-8</encoding>
         </configuration>
       </plugin>