turn doc/tutorial into wiki

[pannous]

Github has the great option to integrate markdown documentation in its project wiki.

If you checkout the default wiki (just add /wiki to your project) you can add it back via git submodule.

All .md files will automatically appear in a dropdown list.

See here for (mediocre) example :
https://github.com/pannous/wasp/wiki <= https://github.com/pannous/wasp/