Releasing version 1.3.1

Change-Id: Iaf1c6c2396a6744113202d786bb236f769147f11
diff --git a/VERSION b/VERSION
index 625610e..3a3cd8c 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.3.1-dev
+1.3.1