obj2stl.py I found on the internet

from https://github.com/pipitone/3Dmodels/blob/master/obj2stl.py

except it doesn't work on my obj file :(
refactor
every possible linetype
only keep the stl writing stuff

I don't need the rest of the original obj2stl script, it wasn't parsing
the correct format.
complete obj2stl

strange, the original script was using writelin, which I don't recognize
as valid python. Anyway, it's fixed now, and I can produce stl files.
ASCII stl output