Update tox testing and docs

Switches to using pyproject.toml and drops poetry

README.md

@@ -195,12 +195,15 @@ The test app can be run to develop your contribution.
 1. Fork the repo and clone it to your computer.
 2. Change to the folder where you cloned it to.
 
-With [poetry](https://python-poetry.org) installed run:
+Set up a virtual environment and install the dependencies.
+
+```bash
+python -m venv .venv
+source .venv/bin/activate
+pip install -e ".[development]"
+```
 
 ```bash
-poetry install
-poetry shell
-# run the migrations, add an admin account and start the app
 python manage.py migrate
 python manage.py createsuperuser
 python manage.py runserver