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/replica_placement_test.go

@@ -0,0 +1,14 @@
+package storage
+
+import (
+	"testing"
+)
+
+func TestReplicaPlacemnetSerialDeserial(t *testing.T) {
+	rp, _ := NewReplicaPlacementFromString("001")
+	new_rp, _ := NewReplicaPlacementFromByte(rp.Byte())
+	if rp.String() != new_rp.String() {
+		println("expected:", rp.String(), "actual:", new_rp.String())
+		t.Fail()
+	}
+}