Bumped version of gRPC to 1.3.1

Change-Id: I7798476bd443a796e0e6a6e149ab8f66435ba4fa
diff --git a/protocols/grpc/proto/BUCK b/protocols/grpc/proto/BUCK
index 8d32ab1..8f1b562 100644
--- a/protocols/grpc/proto/BUCK
+++ b/protocols/grpc/proto/BUCK
@@ -3,7 +3,7 @@
 )
 
 PROTOBUF_VER = '3.2.0'
-GRPC_VER = '1.3.0'
+GRPC_VER = '1.3.1'
 
 COMPILE_DEPS = [
     '//lib:CORE_DEPS',