add region tags to cloudsql example (GoogleCloudPlatform#306)

Author: bshaffer

appengine/flexible/cloudsql/app.php

@@ -15,6 +15,7 @@
  * limitations under the License.
  */
 
+# [START example]
 use Silex\Application;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
@@ -68,5 +69,6 @@
     return new Response(implode("\n", $visits), 200,
         ['Content-Type' => 'text/plain']);
 });
+# [END example]
 
 return $app;