directory structure change to work with glide

glide has its own requirements. My previous workaround caused me some
code checkin errors. Need to fix this.

weed/tools/read_index.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/chrislusf/seaweedfs/weed/storage"
+)
+
+var (
+	indexFileName = flag.String("file", "", ".idx file to analyze")
+)
+
+func main() {
+	flag.Parse()
+	indexFile, err := os.OpenFile(*indexFileName, os.O_RDONLY, 0644)
+	if err != nil {
+		log.Fatalf("Create Volume Index [ERROR] %s\n", err)
+	}
+	defer indexFile.Close()
+
+	storage.WalkIndexFile(indexFile, func(key uint64, offset, size uint32) error {
+		fmt.Printf("key %d, offset %d, size %d, nextOffset %d\n", key, offset*8, size, offset*8+size)
+		return nil
+	})
+}