Update app.py

Thanks for your code.  I got an error running python app.py -- ImportError: No module named flask.ext.wtf.FileField
I got it to run after reading the following: 
https://flask-wtf.readthedocs.org/en/v0.9.5/form.html
http://stackoverflow.com/questions/18297041/im-not-able-to-import-flask-wtf-textfield-and-booleanfield