Add python_requires, fix #134
Add python_requires, fix #134

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