add no-cache header for testing

Signed-off-by: Christopher Guindon <chris.guindon@eclipse-foundation.org>
diff --git a/download.php b/download.php
index 0034b4e..05b9a78 100755
--- a/download.php
+++ b/download.php
@@ -24,6 +24,13 @@
   $Menu = new Menu();
   $Paypal = new Paypal();
   $App->preventCaching();
+
+  $ts = gmdate("D, d M Y H:i:s") . " GMT";
+  header("Cache-Control: no-cache, must-revalidate");
+  header("Pragma: no-cache");
+  header("Last-Modified: ". $ts);
+  header("Expires:" . $ts);
+
   include("_projectCommon.php");
 
   $App->Promotion = FALSE;