Pin maven-{compiler,source}-plugin to latest version

Change-Id: I02161ad9cfb86993ba63582e0d62a11136a552df
diff --git a/pom.xml b/pom.xml
index 8b03c1a..93bd0de 100644
--- a/pom.xml
+++ b/pom.xml
@@ -311,6 +311,7 @@
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-compiler-plugin</artifactId>
+        <version>3.1</version>
         <configuration>
           <source>1.7</source>
           <target>1.7</target>
@@ -318,7 +319,9 @@
         </configuration>
       </plugin>
       <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-source-plugin</artifactId>
+        <version>2.3</version>
         <executions>
           <execution>
             <goals>