Dependencies:
- goreleaser: `go get github.com/goreleaser/goreleaser`
- xgo: `docker pull karalabe/xgo-latest; go get github.com/karalabe/xgo`
- dockerd

make sure gotop builds and runs
update version number in main.go
commit changes
tag commit with version number
push changes
export GitHub token in shell
make sure dockerd is running
run `goreleaser --rm-dist -f build/.goreleaser.yml`
update GitHub release with Darwin builds
update homebrew-gotop
    version numbers (there's 3)
    sha256 (run `sha256sum {archived file}`)
update AUR package version number