Added the mime type for pptx. The new Power point format.
diff --git a/application/config/mimes.php b/application/config/mimes.php
index ea01925..c43f1fc 100644
--- a/application/config/mimes.php
+++ b/application/config/mimes.php
@@ -57,6 +57,7 @@
'mif' => 'application/vnd.mif',
'xls' => array('application/excel', 'application/vnd.ms-excel', 'application/msexcel'),
'ppt' => array('application/powerpoint', 'application/vnd.ms-powerpoint'),
+ 'pptx' => 'application/vnd.openxmlformats-officedocument.presentationml.presentation',
'wbxml' => 'application/wbxml',
'wmlc' => 'application/wmlc',
'dcr' => 'application/x-director',