[HOTFIX] Pin poetry tls error virtualenvs

poetry was updated to v1.2.0 on pypi, and it leads on some problems with TLS CA certificates due to the configuration config virtualenvs.create false. I pinned the poetry version to the one we were using (1.1.5) and added certifi dep for none development envs

• https://github.com/python-poetry/poetry/issues/5977
• https://github.com/python-poetry/poetry/issues/1889

closes #79 (closed)