TODO

* Rakefile
  - Need to 'build' the project by concatenating the scripts together in the
    proper order.

* Types
  - Need a special type to handle uneven division, such that '(/ 1 2)' is
    internally represented as '1/2' until it's coerced into a floating point
    value.  This also includes interpreting values like '1/2' as fractions.

* More special forms
  - case
  - (define _form_ _expr_)
  - lambda
   - mostly done, recursion still iffy

* More primitives
  - boolean?
  - char?
  - display
  - list
  - pair?
    - probably need to implement pairs

  - procedure?
  - sin
  - sqrt
  - string?
  - symbol?
  - vector?

* More compiled functions
  - number->string
    - basic form working
    - still needs radix
    - still needs type checking/error handling
      - 1st arg is not a number
      - 2nd arg is not a number
      - 2nd arg is not a valid radix

* Existing functions
  - Implement type checking for existing function and special form implementations
    - using the appropriate messages

* Learn and implement associative lists

* Learn and implement list mapping

* Interpreter needs to be further separated from the environment
  - need a reset function to clear all user defined values AND/OR
  - need to make an instantiatable class out of it

  - will need to be able to dump and load state (JSON?)