Getting openonu go to work with latest rw-core master

Change-Id: Iab3a1ec7de438cce8b865737d6f34447f1723298
diff --git a/vendor/github.com/cespare/xxhash/go.mod b/vendor/github.com/cespare/xxhash/go.mod
new file mode 100644
index 0000000..10605a6
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/go.mod
@@ -0,0 +1,6 @@
+module github.com/cespare/xxhash
+
+require (
+	github.com/OneOfOne/xxhash v1.2.2
+	github.com/spaolacci/murmur3 v0.0.0-20180118202830-f09979ecbc72
+)