Add version command to show binary build info

[Clivern]

This PR adds a command to show version. goreleaser already pass these info during build time so releases will have them by default from now on.

For manual builds, you can provide them:

$ go build -v -ldflags="-X 'main.version=v1.0.0' -X 'main.commit=46f65914e3b26f7044ffe6842ecce10b58e2c2aa' -X 'main.date=2021-03-21T21:37:16Z' -X 'main.builtBy=goreleaser'"

$ ./revive --version
Current revive version v1.0.0 commit 46f65914e3b26f7044ffe6842ecce10b58e2c2aa, built @2021-03-21T21:37:16Z by goreleaser.

# If not there, it will be unknown
$ go build
$ ./revive --version
Current revive version dev commit none, built @unknown by unknown.

Closes #381

[chavacava]

Hi @Clivern, thanks for the PR
What do you think about implementing the version flag as the other flags were implemented? That way we will also accept -version and --version
Something like

...
	defaultConfigPath := buildDefaultConfigPath()
	var versionFlag bool

	flag.StringVar(&configPath, "config", defaultConfigPath, configUsage)
	flag.Var(&excludePaths, "exclude", excludeUsage)
	flag.StringVar(&formatterName, "formatter", "", formatterUsage)
	flag.BoolVar(&versionFlag, "version", false, versionUsage)
	flag.Parse()

	if versionFlag {
		fmt.Printf(
			"revive version %v commit %v, built @%v by %v.\n",
			version,
			commit,
			date,
			builtBy,
		)
		os.Exit(0)
	}

[Clivern]

@chavacava i am fine with both and it's updated to use flags.
i was trying to separate it from revive run flags to be a command argument but couldn't find a nice way.

[chavacava]

thanks @Clivern !