Package certinject in distros' package repos

[JeremyRand]

It would be useful to package certinject in various distros' package repos.

Hacktoberfest participants:

• Package repos participating in Hacktoberfest meta#77

[JeremyRand]

Removing Hacktoberfest label for now, since we don't currently have an NSIS installer, and non-Windows platforms don't have much use for it.