Update tutorial to use stack script

[menelaos]

No description provided.

[menelaos]

Travis failed due to exceeding the time limit.

[Gabriella439]

Does the header still need the --package turtle part?

[menelaos]

I believe it doesn't.
As part of #2805, an experimental import parser, which works quite well, was implemented in 29df0c4.
Unfortunately, the current stack script documentation does not yet mention this feature.
The relevant parts were written on February 9, 2017 (4984a5a), i.e. about one week before the parser came into existence.

[Gabriella439]

Oh, neat! Thanks for doing this and I learned something new :)