Updated change-log.

Signed-off-by: Taylor Otwell <taylorotwell@gmail.com>

changes.txt

@@ -13,4 +13,5 @@ Changes for 3.1:
 	- Added config, view, and lang loaders.
 	- Moved more stuff into application/start
 	- Removed error.display config options.
-	- Added foreign key support to schema builder.
+	- Added foreign key support to schema builder.
+	- Postgres "unique" indexes are now added with ADD CONSTRAINT