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

Stefano Zacchiroli authored Apr 20, 2013 and Romain Bignon committed Apr 25, 2013

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)

This allows using ./setup.py --url as long as you ignore stderr, for example.

This allows running "make clean", or "make all" without using the
setup.py.

I don't think other distributions use the old naming. Also removing 2.5.