fixed factor signature for applicative exercises
Omit an optional type variable of the Stream.filter method.

The type variable [B] of the fpinscala.lazyness.Stream.filter method
can be omitted.
Add .idea the intellij project directory to .gitignore.
Merge pull request #314 from HappyRay/master

Add .idea the intellij project directory to .gitignore.
Add answer/hint for Chapter 2, Exercise 3
Remove and reorder excercises to match final version of the book.
Merge pull request #318 from Jazzatola/answerfix

Add answer/hint for Chapter 2, Exercise 3
Remove editorial comment
Update 03.answer.scala

Should be `&&` instead of `||`
08.answer.scala was the same as 07.answer.scala for chapter 9
Update and rename 19.answer.scala to 19.answer.markdown
Update 19.answer.markdown
Update 19.answer.markdown
Update 19.answer.markdown
Update README.md
fix for Traverse.mapAccum
Implement unfold via Option fns. Closes #325.
Merge pull request #330 from balajisivaraman/stream-unfold

Implement unfold via Option fns. Closes #325.
Issue #334
Simplify answer to exercise 5.2