Defined numbers one and two as pure functions!

It took a while to walk through the evaluation of (add-1 zero) and
(add-1 one by hand). I was confused by how to deal with the nested
lambdas for the longest time. Sorted after a few experiments in REPL and
re-re-re-readings of the introduced to lambda procedures on page 63 of
the book.

Now working our how to define + in pure functional terms without using
scalar numerals.
Deduced add from procedures add-1, one, and two

With a clue from Chandra Sivaraman's post where I stopped reading after
the point where he says:
"; In retrospect, looking at the definition of add-1 above should
; have provided an instant clue as to Church's scheme."
http://cdfrag.wordpress.com/2013/04/14/sicp-exercise-2-6/