Improve documentation
Improve documentation

* Use :param docstrings like Mikhail did

jessamynsmith/fontbakery,googlefonts/fontbakery,moyogo/fontbakery,graphicore/fontbakery,vitalyvolkov/fontbakery,graphicore/fontbakery,davelab6/fontbakery,googlefonts/fontbakery,moyogo/fontbakery,graphicore/fontbakery,vitalyvolkov/fontbakery,googlefonts/fontbakery,moyogo/fontbakery,vitalyvolkov/fontbakery