Higher order functions now work

- Which means you can do:

(define foo [f] (f 5))
(define bar [a] (+ 1 a))

(foo sin)
(foo (+ 1))
(foo bar)
Implemented Lists

- You can't use them for anything yet, though.
Name changes

- REPLParser -> HispParser
- FunCall -> Call
- Also wrote a Bool type...
Can now define lambdas!
Made the lambda name hashing better