right-to-left parser mode

Hi,

I made attoparsec to parse backward. 

API is highly compatible thanks to type family and new type parameter of Parser.
With `(>*<)` operator parser can be onmidirected!

```haskell
module Data.Attoparsec.ByteString.Char8
-- ...
scientifically :: MonoidalParser d => (Scientific -> a) -> DirParser d a
```

https://github.com/yaitskov/attoparsec-monoidal

What do you think about merging?