fixup! Add Show Univ instance

Author: phadej

base/Data/Universe/Helpers.hs

@@ -23,6 +23,7 @@ module Data.Universe.Helpers (
 import Prelude.Compat
 
 import Control.Applicative (Alternative (..))
+import Data.Foldable (toList)
 import Data.Typeable (Typeable)
 import Data.Semigroup (Semigroup (..))
 import Data.List.Compat
@@ -61,7 +62,7 @@ univUncons :: Univ a -> Maybe (a, Univ a)
 univUncons (Univ [])     = Nothing
 univUncons (Univ (x:xs)) = Just (x, Univ xs)
 
--- | Create 'Univ' from potentiall infinite list
+-- | Create 'Univ' from potentially infinite list.
 univFromList :: [a] -> Univ a
 univFromList = Univ