Add apache commons-lang explicitly in dependency.

- ArrayUtils is part of commons-lang

Change-Id: Ia0b7d3b96c1ab04384d0056b1ae1ec7bc41465ca
diff --git a/pom.xml b/pom.xml
index ad490ea..e975b47 100644
--- a/pom.xml
+++ b/pom.xml
@@ -540,6 +540,11 @@
       <version>1.6</version>
     </dependency>
     <dependency>
+      <groupId>commons-lang</groupId>
+      <artifactId>commons-lang</artifactId>
+      <version>2.6</version>
+    </dependency>
+    <dependency>
       <groupId>com.google.guava</groupId>
       <artifactId>guava</artifactId>
       <version>14.0.1</version>