Normalize constraints parantheses

Both of the following are valid:

```haskell
equals1 :: (Eq a) => a -> a
equals2 :: Eq a => a -> a
```

Some people like the first because it keeps things consistent when you start introducing more constraints. Some people prefer the second because it's fewe characters. But I doubt anyone prefers *both* in the same codebase.

It would be nice to support normalizing to either of these based on the settings.