Added Auth and Session backends

I've added Redis backed Auth and Session backends to this project.

Feel free to suggest preferred cleanup and style guidelines, I'm relatively new to Haskell and would love feedback to improve the code.
That'll do just fine here (it's not exported), but in practice you'd usually want the function to return `Maybe Int` just to ensure you don't make extra implicit assertions you may later lose track of. It can be done with `readInt` from `ByteString.Char8`.