First step for packaging the project

Fix #1 (closed)

Here is the result we have after applying this MR:

$ pip install git+https://gitlab.inria.fr/dpertin/madpp@packaging
Collecting git+https://gitlab.inria.fr/dpertin/madpp@packaging
  Cloning https://gitlab.inria.fr/dpertin/madpp (to revision packaging) to ./pip-req-build-i6gbvuiq
  Running command git clone -q https://gitlab.inria.fr/dpertin/madpp /tmp/pip-req-build-i6gbvuiq
  Running command git checkout -b packaging --track origin/packaging
  Basculement sur la nouvelle branche 'packaging'
  La branche 'packaging' est paramétrée pour suivre la branche distante 'packaging' depuis 'origin'.
Building wheels for collected packages: concerto
  Building wheel for concerto (setup.py) ... done
  Created wheel for concerto: filename=concerto-0.0.1-cp37-none-any.whl size=52028 sha256=d8013027d9349f00a3618c3195e30073e0f0de7d0e757d2dd3f6a4bc39c6e050
  Stored in directory: /tmp/pip-ephem-wheel-cache-ju2gzqy9/wheels/4e/e2/0f/8196de71452a82015bbeda444c78e7a66972f79659e3e928bb
Successfully built concerto
Installing collected packages: concerto
Successfully installed concerto-0.0.1

Packaging requires to manage the project versioning. I propose to respect the semantic versioning specification.