reorg code and add Readme

README.md

@@ -1,3 +1,47 @@
 # command
 
 utils for command line app
+
+Provide two style for command line args parse:
+
+- use struct field tag
+- use command
+
+## Usage
+
+use struct field tag
+
+```go
+type targs struct {
+	Test     string `flag_default:"test" flag_usage:"this is test"`
+	TestBool bool   `flag_short:"b"`
+	TestInt  int
+}
+	sargs := &targs{}
+	v, _ := NewFVSet(sargs)
+	v.Usage()
+	err := Parse([]string{"--test", "test", "--test-bool", "--test-int", "1"}, v)
+```
+
+use command style
+
+```go
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"git.pyer.club/kingecg/command"
+)
+
+func main() {
+	var cmd = command.NewCommand("test", "test command")
+	cmd.AddArg("arg1", "a", "arg1 description", "default value")
+	cmd.AddArg("arg2", "b", "arg2 description", "default value")
+	cmd.AddSubCommand("sub1", "sub1 description")
+	cmd.Parse(os.Args[1:])
+	fmt.Println(cmd.GetGlobalOptions())
+}
+
+```