Update FlatPages import in dead-yet-easy...

For the current version of FlatPages(0.11) you need to import this way. Thanks for the great tutorial!
https://pythonhosted.org/Flask-FlatPages/
additional instance of flatpages import
Merge pull request #5 from wsvincent/patch-1

Update FlatPages import in dead-easy-yet-powerful-static-website-generator-with-flask