python-flask-bootstrap: Add recipe for version 3.3.5.7

It's an extension that includes Bootstrap in your project, without any
boilerplate code.

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>