Updating to grpc 1.13.1

- and make value a parameter

Change-Id: Ib1b6cc23aeac98f3c177f81254bc455c16086875
diff --git a/VERSION b/VERSION
index 437459c..73462a5 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.5.0
+2.5.1