Use XSD

Author: garydgregory

src/changes/changes.xml

@@ -15,7 +15,9 @@
    See the License for the specific language governing permissions and
    limitations under the License.
 -->
-<document>
+<document xmlns="http://maven.apache.org/changes/1.0.0"
+          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+          xsi:schemaLocation="http://maven.apache.org/changes/1.0.0 http://maven.apache.org/xsd/changes-1.0.0.xsd">
   <properties>
     <title>Apache Commons CLI Release Notes</title>
   </properties>