Add vendor

Specifically because I want to modify a dependency

vendor/github.com/atotto/clipboard/clipboard_darwin.go

@@ -0,0 +1,52 @@
+// Copyright 2013 @atotto. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin
+
+package clipboard
+
+import (
+	"os/exec"
+)
+
+var (
+	pasteCmdArgs = "pbpaste"
+	copyCmdArgs  = "pbcopy"
+)
+
+func getPasteCommand() *exec.Cmd {
+	return exec.Command(pasteCmdArgs)
+}
+
+func getCopyCommand() *exec.Cmd {
+	return exec.Command(copyCmdArgs)
+}
+
+func readAll() (string, error) {
+	pasteCmd := getPasteCommand()
+	out, err := pasteCmd.Output()
+	if err != nil {
+		return "", err
+	}
+	return string(out), nil
+}
+
+func writeAll(text string) error {
+	copyCmd := getCopyCommand()
+	in, err := copyCmd.StdinPipe()
+	if err != nil {
+		return err
+	}
+
+	if err := copyCmd.Start(); err != nil {
+		return err
+	}
+	if _, err := in.Write([]byte(text)); err != nil {
+		return err
+	}
+	if err := in.Close(); err != nil {
+		return err
+	}
+	return copyCmd.Wait()
+}