Bump all the edwardk dependencies to >= 4 && < 5.
Renamed things to be more lens-4.0-compatible.

Replaced `Overloading` with `Optical`, `unwrapped` with `_Unwrapped`,
`wrapped` with `_Wrapped'`.

It doesn't quite work yet; I still need to fix a Wrapped instance.
New `Wrapped` instance for `Value a`.

This reveals more type errors. So it goes.
Deleted HasValue. It's neither exported nor used internally.

It was leading to most of the error messages. Maybe this commit will be
reverted by someone who can figure out what it was for. :)
Fixed `Value a`'s `Wrapped` instance.

The order of the `Iso` got switched in the 4.0 bump.

This is the last type error!
Added an example using `Supplementary` keys.