HLint is triggered

[philderbeast]

I ran hlint over rio and rio-orphans and found:

Warnings currently triggered by your code

- [ ] Avoid lambda using `infix`, 1 hint
- [ ] Move brackets to avoid $, 1 hint
- [ ] Redundant $!, 3 hints
- [ ] Redundant <$>, 1 hint
- [ ] Redundant bracket, 2 hints
- [ ] Redundant return, 1 hint
- [ ] Unused LANGUAGE pragma, 5 hints
- [ ] Use const, 4 hints
- [ ] Use fmap, 3 hints
- [ ] Use fold, 1 hint
- [ ] Use newtype instead of data, 1 hint

Which of these do we care about?