Fix requirements for Flask-Autodoc

That package does not work with recent versions of Flask:

webapp_1    |   File "/usr/local/lib/python3.5/site-packages/flask_autodoc/__init__.py", line 3, in <module>
webapp_1    |     from flask.ext.autodoc.autodoc import Autodoc
webapp_1    | ImportError: No module named 'flask.ext'

flask.ext was deprecated some years ago in Flask-0.11 and removed in 1.0,
see http://flask.pocoo.org/docs/1.0/upgrading/.

Nevertheless, Flask-Autodoc still uses flask.ext. See issue
acoomans/flask-autodoc#27.

Signed-off-by: Stefan Weil <sw@weilnetz.de>

requirements.txt

@@ -1,5 +1,6 @@
 # For the HTTP-API
-Flask
+# TODO: Hack, use Flask before 1.0 to work with broken Flask-Autodoc-0.1.2.
+Flask<1.0
 Flask-SQLAlchemy
 Flask-Script
 Flask-Autodoc