FindBugs integration for detecting common errors

Includes the FindBugs maven plugin so that we can spot and fix
common mistakes.

In order to execute FindBugs:
mvn findbugs:findbugs

Change-Id: I342f74b097c69547a567f13433fa97ebd1605c90

pom.xml

diff --git a/pom.xml b/pom.xml
index 1c22a9e..bb5bba5 100644
--- a/pom.xml
+++ b/pom.xml
@@ -247,6 +247,15 @@
       </plugin>
     </plugins>
   </build>
+  <reporting>
+    <plugins>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>findbugs-maven-plugin</artifactId>
+        <version>3.0.0</version>
+      </plugin>
+    </plugins>
+  </reporting>
   <repositories>
     <repository>
       <releases>