Project setup

[exvertus]

Use https://github.com/getpelican/pelican as a model

• tox for test and env management
• poetry package manager and project.toml
  • figure out how/why setup.py is still getting used
• requirements .pip files
• directory layout

[exvertus]

• [x] Finish tox examples
• [x] Add tox config
• [x] Do Poetry research
• [x] Add Poetry config
• [x] Review and complete