Make installable via instawow

[KOVIKO]

Instawow is unable to install from this repository, with this error:

$ instawow install github:wow-addon/FarmIt2
✗ github:wow-addon/FarmIt2
  no files found for: any_flavour=None; any_release_type=None;
    version_eq=None

[Mythris29]

@davidcraig I'm not exactly sure how Wowup and Instawow handle addons but if you look at https://github.com/dartraiden/broker-volume it works as a github addon in Wowup. I think it needs a release in a .zip format to work.