This reverts commit 1fc16b4b.

This builds fine locally but not on my Hydra for some reason.

Fix #779: add missing installation step to README

Ignore 'Unnecessary hiding'

Don't include display modules by default when building with Nix

This improves Nix compatibility without changing Stack or Cabal
compatibility. See #728.

This module takes an incredibly long time to compile and I haven't
missed it. If needed, it can be enabled with e.g.
`--arg packages '(p: [ p.ihaskell-widgets ])'`.

Haddock doesn't seem to work with comments between the module name and
the import statements.