adds vendor directory

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

vendor/github.com/mattn/go-gtk/example/number/number.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"fmt"
+	"github.com/mattn/go-gtk/glib"
+	"github.com/mattn/go-gtk/gtk"
+	"os"
+	"strconv"
+	"unsafe"
+)
+
+func main() {
+	gtk.Init(&os.Args)
+
+	dialog := gtk.NewDialog()
+	dialog.SetTitle("number input")
+
+	vbox := dialog.GetVBox()
+
+	label := gtk.NewLabel("Numnber:")
+	vbox.Add(label)
+
+	input := gtk.NewEntry()
+	input.SetEditable(true)
+	vbox.Add(input)
+
+	input.Connect("insert-text", func(ctx *glib.CallbackContext) {
+		a := (*[2000]uint8)(unsafe.Pointer(ctx.Args(0)))
+		p := (*int)(unsafe.Pointer(ctx.Args(2)))
+		i := 0
+		for a[i] != 0 {
+			i++
+		}
+		s := string(a[0:i])
+		if s == "." {
+			if *p == 0 {
+				input.StopEmission("insert-text")
+			}
+		} else {
+			_, err := strconv.ParseFloat(s, 64)
+			if err != nil {
+				input.StopEmission("insert-text")
+			}
+		}
+	})
+
+	button := gtk.NewButtonWithLabel("OK")
+	button.Connect("clicked", func() {
+		fmt.Println(input.GetText())
+		gtk.MainQuit()
+	})
+	vbox.Add(button)
+
+	dialog.ShowAll()
+	gtk.Main()
+}