Programming Languages - Assignment Two
Written by: Chaskin Saroff
Due: October 7, 2014

Functionality:
    eval-exp takes a binding list and an expression and gives back a simplified expression.

It is called as follows:
    (eval-exp binding-list exp)

A binding list comes in the following form:
    '((oldVal1 newVal1) (oldVal2 newVal2) ... (oldValn newValn))
    
    where oldVal represents a value in an expression exp that will be replaced with newVal.