Deprecate html2text<3.200 and add it to requirements.
This is a light dependency and it is used by a great number of modules.

The syntax for using a metaclass is different in python2 and python3,
and there are existing helpers.

Add six as a dependency in setup.py.

QGalleroob allows to search galleries and images and browse collections
of those.

There should not be an an __init__.py in the modules/ directory.
But in case it gets added, the change in setup.py will prevent
installation.

We don't support python 2.6 anymore

It's used on many modules, add it to the base of requirements

--requires is not it; see
https://mail.python.org/pipermail/distutils-sig/2013-December/023180.html

This should help end-users to install weboob on their systems.

closes #929

rationale: proper build needs to go through setup.py anyhow
by renaming Makefile to a less common name, we avoid people building by mistakes
only the makefile-driven part.

This also helps distribution heuristics when guessing how to auto-build
packages (e.g. Debian dh_auto_build)