Add flux version command

Signed-off-by: Somtochi Onyekwere <somtochionyekwere@gmail.com>

cmd/flux/version_test.go

@@ -1,15 +0,0 @@
-// +build unit
-
-package main
-
-import (
-	"testing"
-)
-
-func TestVersion(t *testing.T) {
-	cmd := cmdTestCase{
-		args:   "--version",
-		assert: assertGoldenValue("flux version 0.0.0-dev.0\n"),
-	}
-	cmd.runTestCmd(t)
-}