Lambda is a lambda calculus interpreter. It also will convert lambda expression
into the combinators S, K, and I.

Current features:
    * Load predefined lambda expression
    * Many definitions provided: numbers Y fact map iszero list 1st 2nd 3rd
      ADD MUL EXP list suc pred . . .
    * Automatic number definitions.
    * Interpret lambda expressions.
    * Single step interpretation.
    * Normal or application order reductions.
    * Variable extraction (Conversion to S K I)
    * List definitions.
    * Some lambda calculus theory.