Test tutorials against solutions at different stages.

[ShMcK]

From @ShMcK on October 9, 2016 18:20

Tests should be verified against a solution.

1. Prevent bugs in tutorials.
2. Users should be able to load this solution state if they get lost or stuck.

This solution state could be:

1. tied to git commit tags (ie. "step01" tag for first step)
2. saved inside of a "solution" directory in each step

Copied from original issue: coderoad/atom-coderoad-deprecated#25