add Scan/Scanf functions for gcmd; improve gfile.IsEmpty

.example/frame/main/model/model1.go

@@ -10,6 +10,4 @@ func main() {
 	user, err := test.ModelUser().One()
 	g.Dump(err)
 	g.Dump(user)
-	user.Password = "1"
-	g.Dump(user.Update())
 }

.example/other/test.go

@@ -1,23 +1,11 @@
 package main
 
 import (
-	"os"
+	"fmt"
 
-	"github.com/olekukonko/tablewriter"
+	"github.com/gogf/gf/os/gcmd"
 )
 
 func main() {
-	data := [][]string{
-		[]string{"1/1/2014", "Domain name", "2233", "$10.98"},
-		[]string{"1/1/2014", "January Hosting", "2233", "$54.95"},
-		[]string{"1/4/2014", "February Hosting", "2233", "$51.00"},
-		[]string{"1/4/2014", "February Extra Bandwidth", "2233", "$30.00"},
-	}
-
-	table := tablewriter.NewWriter(os.Stdout)
-	table.SetBorder(false)
-	table.SetRowLine(false)
-	table.SetColumnSeparator("")
-	table.AppendBulk(data)
-	table.Render()
+	fmt.Println(gcmd.Scan("input:"))
 }