Updated change-log.

Added note about cviebrock's unsigned method.
Signed-off-by: Taylor Otwell <taylorotwell@gmail.com>

changes.txt

@@ -8,4 +8,5 @@ Changes for 3.1:
 	- default value on config::get
 	- Registering of view paths and extensions
 	- Pattern based filters.
-	- Better session ID assignment
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+	- Better session ID assignment
+	- Added cviebrock's unsigned support.
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