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.
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
Prevent unnecessary evaluations

Previous implementation of drop did not handle 
    
    Stream.cons(0, ???).take(1)
Proper comments on take(n) and drop(n)
fix compilation error for 05.answer.scala in chapter 12
Update 05.answer.scala
Update 04.hint.txt
Update 05.hint.txt