Moves the proto to the location within the maven repo

src/main/proto/helloworld.proto

@@ -1,5 +1,7 @@
 syntax = "proto3";
 
+option java_package = "ex.grpc";
+
 package helloworld;
 
 // The request message containing the user's name.
@@ -13,7 +15,7 @@ message HelloReply {
 }
 
 // The greeting service definition.
-service Greeting {
+service Greetings {
   // Sends a greeting
   rpc hello (HelloRequest) returns (HelloReply) {
   }