[ci skip] Add a note about sess_save_path in config.php
diff --git a/application/config/config.php b/application/config/config.php
index cc1307c..f78371f 100644
--- a/application/config/config.php
+++ b/application/config/config.php
@@ -330,6 +330,8 @@
 |	The location to save sessions to, driver dependant.
 |
 |	For the 'files' driver, it's a path to a writable directory.
+|	WARNING: Only absolute paths are supported!
+|
 |	For the 'database' driver, it's a table name.
 |	Please read up the manual for the format with other session drivers.
 |