Update user_agents.php

Added Win 8.1 user agent to the array
diff --git a/application/config/user_agents.php b/application/config/user_agents.php
index 0953dea..3dbf987 100644
--- a/application/config/user_agents.php
+++ b/application/config/user_agents.php
@@ -36,6 +36,7 @@
 */
 
 $platforms = array(
+	'windows nt 6.3'	=> 'Windows 8.1',
 	'windows nt 6.2'	=> 'Windows 8',
 	'windows nt 6.1'	=> 'Windows 7',
 	'windows nt 6.0'	=> 'Windows Vista',
@@ -224,4 +225,4 @@
 );
 
 /* End of file user_agents.php */
-/* Location: ./application/config/user_agents.php */
\ No newline at end of file
+/* Location: ./application/config/user_agents.php */