updated CHANGELOG

CHANGELOG

+version 0.3.1
+--------------
+* FIXED typos in the **README** file
+
 version 0.3.0
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 * CHANGED added informations in the **README**
@@ -8,7 +12,7 @@ version 0.2.0
 * FIXED   typos due to files and classes renamings
 * CHANGED reorganized the files
 * CHANGED reorganized renamed some classes
-* CHANGED added informations in the **README**
+* CHANGED added informations in the **README** file
 
 version 0.1.0
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