make it clear about sort feature

Author: truebit

README.md

@@ -36,7 +36,7 @@ As you may know, the [`UUID`](http://www.ietf.org/rfc/rfc4122.txt) generated by
 5. If you want to use part of xUnique functions, use below options in arguments:
     * `-v`: print verbose output
     * `-u`: uniquify project file, that is, replace UUID to MD5 digest
-    * `-s`: sort project file inlcuding `children` list, `files` list, `PBXFileReference` list and `PBXBuildFile`
+    * `-s`: sort project file inlcuding `children` list, `files` list, `PBXFileReference` list and `PBXBuildFile`. Supports both original and uniquified project file
     * if neither `-u` nor `-s` exists, execute both uniquify and sort
 
 ### Examples