Change version to 1.4.0-dev (#1212)

diff --git a/rpc_util.go b/rpc_util.go
index 2210af3..738cdae 100644
--- a/rpc_util.go
+++ b/rpc_util.go
@@ -496,6 +496,6 @@
 const SupportPackageIsVersion4 = true
 
 // Version is the current grpc version.
-const Version = "1.3.0-dev"
+const Version = "1.4.0-dev"
 
 const grpcUA = "grpc-go/" + Version