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/storage/volume_info_test.go

@@ -0,0 +1,23 @@
+package storage
+
+import "testing"
+
+func TestSortVolumeInfos(t *testing.T) {
+	vis := []*VolumeInfo{
+		&VolumeInfo{
+			Id: 2,
+		},
+		&VolumeInfo{
+			Id: 1,
+		},
+		&VolumeInfo{
+			Id: 3,
+		},
+	}
+	sortVolumeInfos(vis)
+	for i := 0; i < len(vis); i++ {
+		if vis[i].Id != VolumeId(i+1) {
+			t.Fatal()
+		}
+	}
+}