add ex 2.02
add ex 2.03
ignore resources/

* resources/ holds code from each chapter useful in writing tests for
  each exercise.
* these resources are not part of my work, and do not belong in the
  repository.
increase tolerance and show computed value
add ex 1.35 explanation
add ex 1.36 explanation
add ex 1.37 explanation
add ex 1.38 explanation
add ex 1.39 explanation
finish incomplete sentence