Restricting Sphinx version
Restricting Sphinx version

Restricting Sphinx version to 1.6 for RTD to build correctly.

newlawrence/poliastro,anhiga/poliastro,newlawrence/poliastro,Juanlu001/poliastro,Juanlu001/poliastro,anhiga/poliastro,poliastro/poliastro,anhiga/poliastro,Juanlu001/poliastro,newlawrence/poliastro