python-flask-wtf: Add recipe for version 0.12

It's a simple integration of Flask and WTForms.

Signed-off-by: Fabio Berton <fabio.berton@ossystems.com.br>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>