Adding a gitignore
Working on getting the generic looping constructs for the env and frame
Finishing the abstract traversal of the env for the set and lookup
A make-undefined that removes a binding from the current frame only
A primitive repl for our interpreter
Adding an explaination for why the halting problem exists
A modification to lookup that throws an error when an undefined value is found
Converting a set of inner defines into a let statement that will throw an error if you try to use a binding before it has been defined