doc: Point to GitHub for source code

Author: eugmes

doc/index.rst

@@ -20,7 +20,7 @@ Download
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 `python-gdsii` can be downloaded from its Python Package Index `page <http://pypi.python.org/pypi/python-gdsii/>`_.
-The source code repository is available on `gitorious.org <http://gitorious.org/python-gdsii>`_.
+The source code repository is available on `GitHub <https://github.com/eugmes/python-gdsii>`_.
 
 Usage
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