Add SICP exercise 3.1
Add SICP exercise 3.2
Add SICP exercise 3.3
Add SICP exercise 3.4
Update exercise 3.4, decrease local variables
Add SICP exercise 3.5
Add SICP exercise 3.6
Add SICP exercise 3.7
Add SICP exercise 3.8
Add SICP exercise 3.17