How to generate documentation

[j0yu]

Is your feature request related to a problem? Please describe.
Write up on how to generate the documentation and when developing, forcing the CI to generate pages

Describe the solution you'd like
New howto/makedocs.rst outlining setting up venv and modifying .travis.yml (and why generally it is not a good idea)

Additional context

rm -rf ./docs/api/ ./docs/_build/
source /path/to/docs/venv/bin/activate
sphinx-apidoc -o ./docs/api --separate --no-toc ./
sphinx-apidoc -o ./docs/api/hooks --separate --tocfile index ./hooks
sphinx-build ./docs ./docs/_build