Added first version of coordinates.py
Added first version of coordinates.py

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