0.1.0.6

* Implement `ExitcodeT1` which associates the same type of value
* Implement functions over `System.Process` to use exitcode

0.1.0.5

* Large refactor, involving an associated value with an exit failure.
* Delete nix
* Delete Travis CI

0.1.0.4

* Fix `Semigroup` instance.
* Implement `Monoid` instance.

0.1.0.3

* Fix bug in `Extend` instance.
* Remove `Extend` instance.
* Add more constructor functions.

0.1.0.2

* `_ExitSuccess` more polymorphic.

0.1.0.1

* Make `_ExitSuccess` more polymorphic. It was unnecessarily specialised to `()`.
* Use `NoImplicitPrelude` and explicit imports.
* Depend on `mmorph` and implement instances for `MFunctor` and `MMonad`.

0.1.0.0

* This change log starts.
* The initial version of exitcode.