Add remaining haskell book exercises

Haskell-book/17/Combinations.hs

@@ -0,0 +1,12 @@
+module Combinations where
+
+import Control.Applicative (liftA3)
+
+stops :: String
+stops = "pbtdkg"
+
+vowels :: String
+vowels = "aeiou"
+
+combos :: [a] -> [b] -> [c] -> [(a, b, c)]
+combos = liftA3 (\x y z -> (x, y, z))