Update README.md

[ruancomelli]

Currently, the README.md file describes an old version of the project. The main points to change are:

• Installation:
  • installation now should be done preferably using poetry
  • the files requirements.txt, requirements-dev.txt and requirements-scripts.txt no longer exist or are no longer used
  • the command python setup.py install will no longer work since there is no file setup.py
• Contributing: poetry install should be enough to install the necessary development dependencies
• Making changes: the preferable way of running tests and coverage check is running make test and make coverage
• Committing: the current way of committing is by running make commit
• Releasing new versions: to release a new version automatically, the recommended way is running make release
• Upcoming: I should probably include a "how to use" section