meh
Still with classes
Fix Minitest warnings.
Fix parentheses/indentation.
All tests passing using List & Atom classes.
Split file into one per class.
Only the tests with environment lookup make sense at this point.

As per @tomstuart's comment [1]. Removing these tests means we can simplify
`Evaluator#evaluate`.

[1] https://gist.github.com/floehopper/8548547/#comment-991043
DRY up Evaluator#evaluate.
Add test for ( car ( car l ) ) to drive implementation.
Tied them together like a boss
Move implementation into lib/ in preparation for merge
Import the work-in-progress Scheme interpreter