Reverted rui_string change.

This had knock-on effects as can be seen in #1306. Issue #122 has been
reopend until it is fixed properly.
diff --git a/system/core/Router.php b/system/core/Router.php
index fe9909b..9314052 100755
--- a/system/core/Router.php
+++ b/system/core/Router.php
@@ -242,12 +242,9 @@
 			$segments[1] = 'index';
 		}
 
-		// This is being routed to a file in a sub directory
-		$this->directory and array_unshift($segments, trim($this->directory, '/'));
-
 		// Update our "routed" segment array to contain the segments.
 		// Note: If there is no custom routing, this array will be
-		// identical to $this->uri->segments		
+		// identical to $this->uri->segments
 		$this->uri->rsegments = $segments;
 	}