make a new release for compatibility with ghc-8.4.1

[ruomad]

It would be nice to make a release integrating the master commits implementing compatibility with the new base

[BardurArantsson]

@lpsmith I'd also greatly appreciate a release so that I no longer have to vendor my tuple size "fix".

[alpmestan]

Same for servant (one of our cookbook examples uses postgresql-simple, and we build it in CI).

[tomjaguarpaw]

Same for opaleye.

Please let us know if we can be of any help with this!

[phadej]

NMU performed. http://hackage.haskell.org/package/postgresql-simple-0.5.4.0

haskell-infra/hackage-trustees#155

[BardurArantsson]

Very nice, thank you!