Fix warnings and whitespace

Crypto/Number/ModArithmetic.hs

@@ -1,5 +1,4 @@
 {-# LANGUAGE BangPatterns #-}
-{-# LANGUAGE DeriveDataTypeable #-}
 -- |
 -- Module      : Crypto.Number.ModArithmetic
 -- License     : BSD-style
@@ -71,7 +70,7 @@ exponentiation b e m
     | b == 1    = b
     | e == 0    = 1
     | e == 1    = b `mod` m
-    | even e    = let p = (exponentiation b (e `div` 2) m) `mod` m
+    | even e    = let p = exponentiation b (e `div` 2) m `mod` m
                    in (p^(2::Integer)) `mod` m
     | otherwise = (b * exponentiation b (e-1) m) `mod` m