Update user_agents.php

Added the PS Vita User Agent to the list.
diff --git a/application/config/user_agents.php b/application/config/user_agents.php
index 35c36cb..db75c81 100644
--- a/application/config/user_agents.php
+++ b/application/config/user_agents.php
@@ -149,6 +149,7 @@
 	'mot-'			=> 'Motorola',
 	'playstation portable'	=> 'PlayStation Portable',
 	'playstation 3'		=> 'PlayStation 3',
+	'playstation vita'  	=> 'PlayStation Vita',
 	'hiptop'		=> 'Danger Hiptop',
 	'nec-'			=> 'NEC',
 	'panasonic'		=> 'Panasonic',
@@ -218,4 +219,4 @@
 );
 
 /* End of file user_agents.php */
-/* Location: ./application/config/user_agents.php */
\ No newline at end of file
+/* Location: ./application/config/user_agents.php */