Implement #forAll
Implement #takeWhile as foldRight and #headOption
Implement #map using foldRight
Implement #append using foldRight
Implement #append, #constant, #from and #fibs
Implement #unfold
Implement .onesUnfold, .constantUnfold and .fibsUnfold
Implement #mapUnfold
Implement #takeUnfold
Implement #takeWhileUnfold
Implement #zipWithUnfold
Implement #tails