added propagation tests (no parabolic yet)
added propagation tests (no parabolic yet)

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