refactor how repl works

internal/object/state.go

@@ -1,10 +1,14 @@
 package object
 
-import "io"
+import (
+	"io"
+	"os"
+)
 
 var (
-	Arguments      []string
-	StandardInput  io.Reader
-	StandardOutput io.Writer
-	ExitFunction   func(int)
+	Args         []string  = os.Args
+	Stdin        io.Reader = os.Stdin
+	Stdout       io.Writer = os.Stdout
+	Stderr       io.Writer = os.Stderr
+	ExitFunction func(int) = os.Exit
 )