Steenzout-sphinx

- removed `sphinx.ext.imgmath` extension since it causes problems with [readthedocs.org](https://readthedocs.org/)
- docstring change

- automate apidoc generation as proposed https://github.com/rtfd/readthedocs.org/issues/1139

- initial release
- templates for
- `conf.py`
- `Makefile`
- `steenzout-sphinx-generate` command-line interface