Support new goreleaser versions and installation via Homebrew

Motivation

As a maintainer, I use the goreleaser to build and publish binaries
of my tools and services. But the godownloader is no longer actively maintained and
doesn't support new goreleaser configurations. I need to adapt it to new versions
of goreleaser and generate actual installation shell scripts.

As a developer, I want to install the godownloader using Homebrew or
a shell script generated by it. But the godownloader doesn't support that.
I need to add support for new goreleaser versions and Homebrew.

What's changed

• The godownloader supports new versions of goreleaser¹.
• The tool is available by brew install octolab/tap/godownloader.
• The installation is also possible by

  $ curl -sSfL https://install.octolab.org/godownloader | sh -s -- -b /usr/local/bin

Related issues

• goreleaser#161
• goreleaser#207
• goreleaser/godownloader@master...kamilsk:extended

made with ❤️ for everyone by OctoLab

1. Limited support, tested only with go-tool and go-service. ↩