hailgun-0.5.0: Changelog.md

## 0.5.0

- [PR #26](https://bitbucket.org/echo_rm/hailgun/pull-requests/26/) Support named emails

## 0.4.3

- Fix build for lts-15.1 and time-1.9.3

## 0.4.2

- Adds `Mail.Hailgun.Internal` module, which exposes private APIs for constructing a `HailgunMessage`.