Move per-lesson/stage files out of salt image

[Mierdin]

In #235 it was discovered that there were a few lesson/stage specific files being added to the Salt image. Not a big deal in the grand scheme of things, but we're going to try to make images more reusable in the curriculum, so we will want to circle back and update the entire salt lesson to incorporate these files in the lesson directory as opposed to being baked into the image.