Bumped version of gRPC to 1.3.1

Change-Id: I7798476bd443a796e0e6a6e149ab8f66435ba4fa
diff --git a/bucklets/grpc.bucklet b/bucklets/grpc.bucklet
index 34b31f2..53ab5ef 100644
--- a/bucklets/grpc.bucklet
+++ b/bucklets/grpc.bucklet
@@ -3,7 +3,7 @@
 
 
 DEFAULT_PROTOC_VERSION = '3.2.0'
-DEFAULT_GRPC_PLUGIN_VERSION = '1.3.0'
+DEFAULT_GRPC_PLUGIN_VERSION = '1.3.1'
 
 PROTOC_RELEASE_BASE_URL = "https://github.com/google/protobuf/releases/download"
 GRPC_PLUGIN_BASE_URL = "https://repo1.maven.org/maven2/io/grpc/protoc-gen-grpc-java"
@@ -16,8 +16,8 @@
 }
 
 GRPC_JAVA_SHA1S = {
-    "protoc-gen-grpc-java-1.3.0-linux-x86_64.exe":"44a0fa3e6074852ea84f93d258233b3f4f6d9e53",
-    "protoc-gen-grpc-java-1.3.0-osx-x86_64.exe":"61a1b81b9f0af7d0900c314a4201972b52fb5f12"
+    "protoc-gen-grpc-java-1.3.1-linux-x86_64.exe":"9598b00ad0f41a6bd6aeb01f647903dbc62792cc",
+    "protoc-gen-grpc-java-1.3.1-osx-x86_64.exe":"f4eccb96524b8b9f152024890550d9b88398b8cd"
 }
 
 #Returns the string for the OS and architecture of the system of the form 'OS-ARCH'