Make MinioT monad transformer

Hello!

It would be great, if Minio monad was implemented as a monad transformer, probably, like so:
```haskell
newtype MinioT m a = Minio { unMinio :: ReaderT MinioConn (ResourceT m) a }

runMinioWith :: (MonadIO m) => MinioConn -> Minio m a -> m (Either MinioErr a)
... and so on
```

I already forked this library, and I will let you know if I get anything working.