Delete vendored code and update CI to Go 1.13 (#158)

As the Go community transitions to using the modules ecosystem,
we want to only support one way of managing dependencies.
So this change moves to only using Go modules for dependency management.

This means that our effective minimum Go version increases to Go 1.11.
To account for this, we also update:
  - the documentation
  - Makefile
  - CI scripts

1 files changed, 0 insertions, 22 deletions

diff --git a/vendor/github.com/urfave/cli/cli.go b/vendor/github.com/urfave/cli/cli.go
deleted file mode 100644
index 90c07eb..0000000
--- a/vendor/github.com/urfave/cli/cli.go
+++ /dev/null
@@ -1,22 +0,0 @@
-// 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