squash merge from dev branch

vendor/gopkg.in/alecthomas/kingpin.v2/_examples/modular/main.go

@@ -0,0 +1,30 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"gopkg.in/alecthomas/kingpin.v2"
+)
+
+// Context for "ls" command
+type LsCommand struct {
+	All bool
+}
+
+func (l *LsCommand) run(c *kingpin.ParseContext) error {
+	fmt.Printf("all=%v\n", l.All)
+	return nil
+}
+
+func configureLsCommand(app *kingpin.Application) {
+	c := &LsCommand{}
+	ls := app.Command("ls", "List files.").Action(c.run)
+	ls.Flag("all", "List all files.").Short('a').BoolVar(&c.All)
+}
+
+func main() {
+	app := kingpin.New("modular", "My modular application.")
+	configureLsCommand(app)
+	kingpin.MustParse(app.Parse(os.Args[1:]))
+}