Add remaining haskell book exercises

Haskell-book/17/Identity.hs

@@ -0,0 +1,9 @@
+newtype Identity a = Identity a
+    deriving (Eq, Show, Ord)
+
+instance Functor Identity where
+    fmap f (Identity x) = Identity $ f x
+
+instance Applicative Identity where
+    pure x = Identity x
+    (Identity f) <*> (Identity y) = Identity $ f y