Upstream `v0.4.0` tag has been pushed, `debian/0.4.0-1` has been tagged, the `debian/changelog` has been updated on the debian branch, and I've verified that the package built by `make -f debian/Makefile` installs correctly. We should just need a rebuild for the debian repositories.
Changelog:
```
blubber (0.4.0-1) unstable; urgency=medium
[ Dan Duvall ]
* Provide a CONTRIBUTING.md guide
* Include git as a build dependency
* Introduce strict/versioned config parsing
* Refactor validation tests without YAML parsing
* Ensure non-interactive front-end for APT
[ Alexandros Kosiaris ]
* Add a pip install step
[ Gilles Dubuc ]
* Add support for Builder arbitrary build commands
[ Dan Duvall ]
* Refactor config for node app dependencies
[ Gilles Dubuc ]
* Add now mandatory version config field to README
[ Dan Duvall ]
* Bump config version to v2
[ Tyler Cipriani ]
* Cross-compile using gox
[ Dan Duvall ]
* Attempt to resolve symlinked CURDIR in Makefile
* Release v0.4.0
-- Dan Duvall <dduvall@wikimedia.org
```