[tox] Enable all applicable py34 environments All except etwist. Comes with a few tricks in tox.ini: * add ``-e.`` to force installing of cubicweb in development because dependency cubes would otherwise install cubicweb 3.22 (the latest release), which is not python3 installable. * "install" cubes/__init__.py because the file is not installed in develop mode; maybe this file should be managed by cubes themselves...

missing-dep-for-interpreter make => make | build-essential | dpkg-dev (usr/*/cubicweb/skeleton/debian/rules.tmpl)