Fixed typo reported by Bennett Benson

<BennettBenson@mn.mediaone.net>.

Doc/tut/tut.tex

@@ -149,7 +149,7 @@ explained.  This is rather mundane information, but essential for
 trying out the examples shown later.
 
 The rest of the tutorial introduces various features of the Python
-language and system though examples, beginning with simple
+language and system through examples, beginning with simple
 expressions, statements and data types, through functions and modules,
 and finally touching upon advanced concepts like exceptions
 and user-defined classes.