Add Makefile / .drone.yml, use go module with vendor (#20)

* add Makefile / .drone.yml, use go module with vendor

* Update .drone.yml

Co-Authored-By: lunny <xiaolunwen@gmail.com>

vendor/github.com/urfave/cli/cli.go

@@ -0,0 +1,22 @@
+// Package cli provides a minimal framework for creating and organizing command line
+// Go applications. cli is designed to be easy to understand and write, the most simple
+// cli application can be written as follows:
+//   func main() {
+//     cli.NewApp().Run(os.Args)
+//   }
+//
+// Of course this application does not do much, so let's make this an actual application:
+//   func main() {
+//     app := cli.NewApp()
+//     app.Name = "greet"
+//     app.Usage = "say a greeting"
+//     app.Action = func(c *cli.Context) error {
+//       println("Greetings")
+//       return nil
+//     }
+//
+//     app.Run(os.Args)
+//   }
+package cli
+
+//go:generate python ./generate-flag-types cli -i flag-types.json -o flag_generated.go