Update Graphviz download link.
@@ -106,7 +106,7 @@ Setting up
Make sure you download and install:
- `Python 3.4+ and Python 2.7 <http://www.python.org/downloads/windows/>`_
- - `Graphviz <http://www.graphviz.org/Download_windows.php>`_
+ - `Graphviz <https://www.graphviz.org/download/>`_
Pip should be installed by default with the latest Python installers. Make sure you do not
uncheck the option. When finished installing, open a command prompt.
