Ensure JDK5 compatibility. Fixes #392.
diff --git a/pom.xml b/pom.xml
index 6388e9a..a5eb85f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -43,6 +43,28 @@
         </configuration>
       </plugin>
       <plugin>
+      	<!-- this plugin allows us to ensure Java 5 API compatibility -->
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>animal-sniffer-maven-plugin</artifactId>
+        <version>1.9</version>
+        <executions>
+          <execution>
+            <id>animal-sniffer</id>
+            <phase>compile</phase>
+            <goals>
+              <goal>check</goal>
+            </goals>
+            <configuration>
+              <signature>
+                <groupId>org.codehaus.mojo.signature</groupId>
+                <artifactId>java15</artifactId>
+                <version>1.0</version>
+              </signature>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-javadoc-plugin</artifactId>
         <version>2.6.1</version>