issue #97 modification of session timeout mechanism

fixed unexisted session direcrory behavior.

Author: or

config.sample.php

@@ -14,8 +14,9 @@
 // this defines, where session files will be stored.
 // it is important in this case: http://php.net/manual/en/session.configuration.php#ini.session.gc-maxlifetime
 $currentSessionPath = ini_get('session.save_path');
-$subPath = 'rockmongo';
-ini_set('session.save_path', $currentSessionPath . DIRECTORY_SEPARATOR . $subPath);
+$save_path = $currentSessionPath . DIRECTORY_SEPARATOR . 'rockmongo';
+if (!is_dir($save_path)) mkdir($save_path, 0777, true);
+ini_set('session.save_path', $save_path);
 
 $MONGO = array();
 $MONGO["features"]["log_query"] = "on";//log queries