servermon module + modernize

This fairly large changes attempts to modernize servermon a bit:

* move most files under directory `servermon`. This break the Makefile
  completely :(
* use pbr, a wrapper around setuptools
* MANIFEST.in
* list packages dependencies in requirements.txt and
  test-requirements.txt
* creates a tox environnement to easily run tests. Targets include:
  flake8: run pep8 and pyflakes (currently failing). Ignores lines being
          too long (pep8 E501).
  doc: ported doc targets from the MakeFile.
  py27: attempts to run 'python manage.py test --noinput' with a sqlite3
        database.