Use mkLE instead of LE

[nomeata]

Another step towards #26:

--- haskell-cryptonite-0.6.orig/Crypto/Cipher/ChaChaPoly1305.hs
+++ haskell-cryptonite-0.6/Crypto/Cipher/ChaChaPoly1305.hs
@@ -108,5 +108,5 @@ finalize :: State -> Poly1305.Auth
 finalize (State _ macState aadLength plainLength) =
     Poly1305.finalize $ Poly1305.updates macState
         [ pad16 plainLength
-        , either (error "finalize: internal error") id $ P.fill 16 (P.putStorable (LE aadLength) >> P.putStorable (LE plainLength))
+        , either (error "finalize: internal error") id $ P.fill 16 (P.putStorable (toLE aadLength) >> P.putStorable (toLE plainLength))
         ]

With this and #30 applied, the test suite goes through. I hope it is comprehensive enough that this makes it likely that all endianness-bugs are fixed...

[vincenthz]

good catch: my own mixup on what LE / toLE represented.

Thanks,
Edit: can you make it a Pull request, as that simplify the attribution of the code fix to the rightful owner.