Implement blackbox in Golang (#250)

* Initial release

cmd/blackbox/blackbox.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	_ "github.com/StackExchange/blackbox/v2/pkg/crypters"
+	_ "github.com/StackExchange/blackbox/v2/pkg/crypters/_all"
+	_ "github.com/StackExchange/blackbox/v2/pkg/vcs"
+	_ "github.com/StackExchange/blackbox/v2/pkg/vcs/_all"
+)
+
+var dryRun bool
+
+func main() {
+	app := flags()
+	err := app.Run(os.Args)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "ERROR: %s\n", err)
+		os.Exit(1)
+	}
+}