Mention libraries support explicitely.

README.txt

@@ -49,9 +49,19 @@ Installation
   by cloning.
 - Go to import/ to import data.
 - To use SimplePie parser, download SimplePie and place simplepie.inc into
-  feeds/libraries
+  feeds/libraries.
   http://simplepie.org/
 
+Libraries support
+=================
+
+If you are using Libraries module, you can place external libraries in the
+Libraries module's search path (for instance sites/all/libraries. The only
+external library used at the moment is SimplePie.
+
+Libraries found in the libraries search path are preferred over libraries in
+feeds/libraries/.
+
 API Overview
 ============