adds gitignore to ignore backup files
adds exercise 1.1, just testing basic REPL behaviour
adds exercise 1.2, modelling an expression
adds exercise 1.3, sum of squares of two largest numbers in given three
adds exercise 1.4, demonstrating operators and other elem behave similarly
adds exercise 1.5
adds example 1.1.7, square roots by newton's methods
adds exercise 1.6, demonstrating if is a special form
adds Counting Change example from 1.2.2
adds exercise 1.11
adds exercise 1.12, calculating elements of the Pacscal Triangle
moved files to new subdir - sicp
merges sicp ch1