- Modularize all the builtins, a cleaner framewpork in general.

- Lisp error framework that isn't python assert statements.... That means,
    subclass LispException some more and use try/except statements to actually
    use them.

- add if and maybe cond to the builtin macros

- add lambda (shouldn't be too hard since defun works)

- add let if I feel ambitious with the variable-namespace system