Add persistent undo as the option

cmd/micro/stack_test.go

@@ -1,39 +0,0 @@
-package main
-
-import "testing"
-
-func TestStack(t *testing.T) {
-	stack := new(Stack)
-
-	if stack.Len() != 0 {
-		t.Errorf("Len failed")
-	}
-	stack.Push(5)
-	stack.Push("test")
-	stack.Push(10)
-	if stack.Len() != 3 {
-		t.Errorf("Len failed")
-	}
-
-	var popped interface{}
-	popped = stack.Pop()
-	if popped != 10 {
-		t.Errorf("Pop failed")
-	}
-
-	popped = stack.Pop()
-	if popped != "test" {
-		t.Errorf("Pop failed")
-	}
-
-	stack.Push("test")
-	popped = stack.Pop()
-	if popped != "test" {
-		t.Errorf("Pop failed")
-	}
-	stack.Pop()
-	popped = stack.Pop()
-	if popped != nil {
-		t.Errorf("Pop failed")
-	}
-}