Fix FutureTest code.

Adding methods to package object trumps the ones of the
same name formerly imported.
fix take and takeViaUnfold - don't initialize tail for last taken element
fix take and takeViaUnfold - don't initialize tail for last taken element
Fixed syntax
Merge pull request #287 from AlexanderDaniel/answerkey_monad_exercise6

Fixed syntax in answer key for monads exercise 6
Monads: compose in terms of join
Merge pull request #290 from AlexanderDaniel/composeInTermsOfJoin

Monads: compose in terms of join
Merge pull request #272 from paulp/iomonad-fix

Fix FutureTest code.
Merge pull request #270 from jozic/fix-takeViaUnfold

fix takeViaUnfold - decrease n and don't initialize tail for last taken element