adding List function to memmapfs

memmap.go

diff --git a/memmap.go b/memmap.go
index d820502..2474a3f 100644
--- a/memmap.go
+++ b/memmap.go
@@ -15,6 +15,7 @@
 
 import (
 	"errors"
+	"fmt"
 	"os"
 	"path"
 	"path/filepath"
@@ -257,3 +258,10 @@
 	}
 	return nil
 }
+
+func (m *MemMapFs) List() {
+	for _, x := range m.data {
+		y, _ := x.Stat()
+		fmt.Println(x.Name(), y.Size())
+	}
+}