initial commit ch04
ex 4.1 initial commit
ex 4.1
ex 4.1 revised
ex 4.2
ex 4.4
ex 4.5
ex 4.4

Conflicts:
	src/main/scala/fpinscala/errorhandling/Option.scala
	src/main/scala/fpinscala/errorhandling/OptionWS.sc
typos
initial Either commit
ex 4.6/4.7
closing ch04 commit