func CORS() vodka.MiddlewareFunc {
	return CORSWithConfig(DefaultCORSConfig)
}
CORS returns a Cross-Origin Resource Sharing (CORS) middleware.
See: https://developer.mozilla.org/en/docs/Web/HTTP/Access_control_CORS
package middleware
import (
	"net/http"
	"strconv"
	"strings"
	"github.com/insionng/vodka"
)
type (
	CORSConfig struct {
		Skipper Skipper
		AllowOrigins []string `json:"allow_origins"`
		AllowMethods []string `json:"allow_methods"`
		AllowHeaders []string `json:"allow_headers"`
		AllowCredentials bool `json:"allow_credentials"`
		ExposeHeaders []string `json:"expose_headers"`
		MaxAge int `json:"max_age"`
	}
)
var (
	DefaultCORSConfig = CORSConfig{
		Skipper:      defaultSkipper,
		AllowOrigins: []string{"*"},
		AllowMethods: []string{vodka.GET, vodka.HEAD, vodka.PUT, vodka.PATCH, vodka.POST, vodka.DELETE},
	}
)