adds vendor directory

vendors dependencies in standard `vendor` directory, managed by glide

vendor/github.com/mattn/go-gtk/example/builder/callback/callback.go

@@ -0,0 +1,37 @@
+package callback
+
+import (
+	"unsafe"
+
+	"github.com/mattn/go-gtk/glib"
+	"github.com/mattn/go-gtk/gtk"
+)
+
+var aboutdialog *gtk.AboutDialog
+
+func Init(builder *gtk.Builder) {
+	aboutdialog = &gtk.AboutDialog{
+		*(*gtk.Dialog)(unsafe.Pointer(&builder.GetObject("aboutdialog1").Object))}
+	builder.ConnectSignalsFull(func(builder *gtk.Builder, obj *glib.GObject, sig, handler string, conn *glib.GObject, flags glib.ConnectFlags, user_data interface{}) {
+		switch handler {
+		case "on_imagemenuitem1_activate":
+			obj.SignalConnect(sig, on_imagemenuitem1_activate, user_data, flags)
+		case "on_show_aboutdialog_activate":
+			obj.SignalConnect(sig, on_show_aboutdialog_activate, user_data, flags)
+		case "gtk_widget_hide":
+			obj.SignalConnect(sig, func(c *glib.CallbackContext) {
+				gtk.WidgetFromObject(c.Target().(*glib.GObject)).Hide()
+			}, nil, flags)
+		}
+	}, nil)
+}
+
+//export on_imagemenuitem1_activate
+func on_imagemenuitem1_activate() {
+	gtk.MainQuit()
+}
+
+//export on_show_aboutdialog_activate
+func on_show_aboutdialog_activate() {
+	aboutdialog.Run()
+}