Log Message:
Update to 4.0.4

CHANGELOG from http://github.com/ekmett/semigroupoids
4.0.4
-----
* `contravariant` 1.0 support.

4.0.3
---
* Added flags to provide unsupported cabal sandbox build modes.

4.0.1
-----
* Fixed bitrot in the `Data.Functor.Extend` documentation.
* Fixed warnings on GHC 7.8.1rc2 caused by importing `Control.Monad.Instances`.