Update user_agents.php

Added Ubuntu Web Browser. More info here:
http://www.omgubuntu.co.uk/2013/11/ubuntu-touch-browser-finally-given-unique-user-agent-string
diff --git a/application/config/user_agents.php b/application/config/user_agents.php
index 899e96a..0686bf9 100644
--- a/application/config/user_agents.php
+++ b/application/config/user_agents.php
@@ -104,7 +104,8 @@
 	'hotjava'		=> 'HotJava',
 	'amaya'			=> 'Amaya',
 	'IBrowse'		=> 'IBrowse',
-	'Maxthon'		=> 'Maxthon'
+	'Maxthon'		=> 'Maxthon',
+	'Ubuntu'		=> 'Ubuntu Web Browser'
 );
 
 $mobiles = array(
@@ -223,4 +224,4 @@
 );
 
 /* End of file user_agents.php */
-/* Location: ./application/config/user_agents.php */
\ No newline at end of file
+/* Location: ./application/config/user_agents.php */