add colorable command

cmd/colorable/colorable.go

@@ -0,0 +1,12 @@
+package main
+
+import (
+	"io"
+	"os"
+
+	"github.com/mattn/go-colorable"
+)
+
+func main() {
+	io.Copy(colorable.NewColorableStdout(), os.Stdin)
+}